FME Transformers-Five Unsung Heroes

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Author: Ciara Beddy, IMGS Senior GIS Engineer


 

For a new user looking at FME’s hundreds of available transformers, many with some interesting and unusual names, locating the transformer you need to get the job done can often feel like a difficult or daunting task.As an FME professional and Trainer I often get told in panic “I don’t think I will know what Transformer to use, there are so many!!” and that is true. In reality you can still be a proficient user of FME without knowing the ins and outs of every single Transformer. That is, if you arm yourself with the most useful ones!

Transformer knowledge comes down to experience. The more workspaces you create and projects you complete the larger your catalogue of Transformers becomes. To get new users started I would like to share with you a list of some of the unsung heroes of the transformer world, these are some of the tools I really couldn’t live without.

Reprojector

I am most often asked about how to quickly move spatial data between different coordinate systems. The answer is very simple, use the Reprojector. FME’s coordinate reprojection capabilities solve the common requirement to reproject data accurately and seamlessly. All you are required to do is place the transformer somewhere within your workflow.

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This transformer works on both raster and vector data, It provides the option to reproject data with a library of over 5000 coordinate reference systems. This gives you the ability to reproject data with the click of a button eliminating all those coordinate system headaches you face as a spatial data user.

 

Clipper

The Clipper is an excellent transformer for creating datasets that are relevant to your needs. Often users have national datasets containing more data than they actually require. The Clipper takes a number of clip boundaries and the number of features to be clipped and splits the data into features inside the boundary and features outside the boundary.

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As the output is split into these two possible groups the Clipper allows you to keep the data relevant to your needs while disregarding the data that falls outside your defined boundaries. It is a great way of cleansing your datasets to only contain the data you will use, meaning any further analysis on these datasets are correct and more meaningful to your area of interest.

 

 Counter

If you ever come across the need to provide a unique ID to the data running through your workspace than the Counter is the most simple way to achieve this. This transformer adds a numeric attribute to your features by assigning each feature an incremented value as it counts the features passing through.

5You can also specify if this counter sequence is unique throughout the whole workspace by using the same sequence on multiple counter transformers or using a unique sequence to that single counter. This transformer means you can create unique values without using any complex expressions, calculators or calling database sequences.

 

 

Duplicate Remover

Another key quality control task it to check your data for duplicates, sometimes no matter how ‘perfect’ you think your data is, an unwanted duplicate can creep in during a processing task. FME gives you the ability to ensure that your data is clean by eliminating all those duplicate objects so only one remains. The answer comes in the form of the appropriately name DuplicateRemover. This transformer allows you to select one or multiple key attribute values that you require to be unique. Any key attribute value that has already been encountered in the DuplicateRemover is sent to a separate port labelled as a duplicate.

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Allowing you to maintain the data stream coming from the unique port, giving you confidence in the quality of your output data.

 

LabelPointReplacer

Lastly, users are often tasked with the requirement to provide labels with their output data. There are a number of options in FME for labelling the most basic being the LabelPointReplacer. This transformer enables you to quickly configure labels and rules that will dictate how labels appear.

This transformer replaces the geometry of the coming feature with a label point while also giving you a number of options to define the label value.

If the feature was already a point, it is turned into a text feature at that location.

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  • If the feature was a line, it is turned into a point text feature at the midpoint of the line and rotated parallel to the line.
  • If the feature was an area feature, the resulting point is placed in the interior of the feature.

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The LabelPointReplacer removes the hassle of creating labels for your spatial data and should be your first stop when tackling label requirements.

These are some of the key transformers I regularly use when tackling data problems. Hopefully it will give new users a head start on which of the transformers they may want to try out in the future. But don’t forget if you are ever in doubt or lost on what is the transformer for the job;

  • Use the associated Help File– Every transformer you select will link to the help file which pops up in the help tab in your workspace. If you are unsure of how to use a certain transformer the help file gives you detailed information on the use of the transformer and how to configure the parameters, input and output ports.

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  • Use the Transformer search functionality in the Transformer Gallery to pinpoint your possible transformer options. This searches in both Transformer name and description so your search term may be the exact name of a transformer, or it may be a general keyword referring to functionality.

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  • If all else fails then just try it out, trial and error can often be the best option in understanding exactly how each transformer effects your data. Don’t worry you won’t do any damage to your dataset and can run your workspace as many times as you wish. Just connect an inspector transformer to the end of your workflow instead of connecting it to the writer and you can keep testing until you get it right!

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Also help is always at hand just contact us at support@imgs.ie for FME related queries we are happy to point you in the right direction when you are lost in a maze of Transformer options.

Geospatial Portal – Locate a coordinate

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Author: Vijay Sambhe, Senior Applications Engineer at IMGS


Hexagon’s Geospatial Portal – Locate a coordinate in the Map

Hexagon’s Geospatial Portal is a full-featured, configurable and customisable thin client application that can be used for finding, viewing, querying, analysing, and consuming geospatial data published by Hexagon Geospatial products and/or other standard-based web services. The portal can be accessed by multiple users via web browsers as it is installed and configured on a web application server.

You can easily create custom functionality in the portal using JavaScript. The example shown here is developed using EXTJS. Ext JS is a pure JavaScript application framework for building interactive cross platform web applications using techniques such as Ajax, DHTML and DOM scripting. Originally built as an add-on library extension of YUI by Jack Slocum April 15, 2007, Ext JS includes interoperability with jQuery and Prototype.

I have created a sample application using the JavaScript coding – Locate a coordinate in the map.  In the form, the user is asked to enter coordinate details and the scale at which the zoom is needed.

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When the Locate button is clicked the map zooms in to the location and also it shows the message as shown below.

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Again, this is all done via a client side coding on instance service website which was pretty simple. Create your own JavaScript file and add the reference in the full.aspx by simply editing the file in the notepad editor.

Plenty of help and code examples are available on Hexagon’s Knowledge base here.

Asset Management System with Hexagon’s GeoMedia Smart Client

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Author: Ciarán Kinane, Applications Engineer at IMGS


Hello everyone and welcome to this month’s blog. This month we are going to focus on map based asset management using hexagon’s GeoMedia Smart Client.

                Nowadays people can see the value of GIS within your organization, but they often lack the expertise to run a desktop GIS. Online maps delivered by a web GIS solution are helpful, but these implementations in many cases do not support specific geospatial workflows required by the user. They also may not provide some of the main functionality of a desktop GIS such as snapping etc. Today, users look more and more for market-focused workflows specified to their needs.

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The vast majority of people who could really benefit from geospatial data need more than what a lightweight, browser-based web map can deliver. Likewise, they don’t have the time or expertise to learn a technically demanding desktop environment. These users are eager to geospatially accelerate their business workflows and ignite the power of GIS. This requires a new approach, working outside limiting departmental deployments of GIS that have plagued organizations for decades.

This is where GeoMedia Smart Client comes in. It provides a platform for users which is easy to use and does not require the same training or knowledge required by a desktop GIS. Smart Client is delivered to users via a browser and runs on the client machine using Java. The thing I really like about Smart Client is that it only requires 1 license whether you have 5 users or 500 users running concurrently. Smart Client has the ability to open up GIS to your whole organisation.

Here in IMGS we have provided separately configured asset management systems to both Shannon Properties PLC and Sligo County Council using Hexagon Geospatial’s Smart Client. Out of the box functionality provides, measurement, dimensioning, snapping, redlining and configurable printing, but the real power in Smart Client is the ability to create interactive workflows to meet the user’s needs.

Asset Register

For Sligo County Council we used Smart Client to replace their fully customized map based asset management solution. Using Workflow Manager, which comes with the professional version of Smart Client, we were able to create an Asset Search workflow.

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The Asset Search has the ability to filter on multiple attributes within the asset database. For each entry returned in the search, we have the ability to map to, edit or view that asset and sort by any attribute. The asset list can also be printed to csv, excel, word or PDF and can include XY coordinates of the asset, criteria which are a requirement of the Office of Public Works in Ireland.

We also created a workflow which allows the user add a new asset to their system. When the user selects the ‘NEW’ button they are presented with a form whereby the user can enter details pertaining to the asset. The workflow can have many rules to prompt and aid the user with the compiling of asset details. For example, the user can enter no more than 5 digits as the asset number, or the asset ID can be created based on the asset number with a prefix coincident with the asset type specified in a drop down box.

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Once the user has entered in the minimum details, they can begin to digitizing the asset in the map window.

While digitizing, the user is afforded many features which would not be available within a web based mapping solution, such as snapping to vector data (as seen on the image below), dimensioning and the ability to scroll the map while in capture mode etc.Asset Register4.png

Various geometry rules can be applied at this point to guide the users. For instance in the Shannon Properties project they requested some rules which would not allow the user to capture the boundary of a building outside the boundary of a particular site. Another rule requested was to not allow the user to capture the boundary of a site outside a particular Landbank feature. These rules can be applied and guides set in place to direct the user reducing anomalies in the data and standardising your digitizing processes.

Once captured in the map window, the user is brought back to the workflow where they can enter additional details into attribute fields. The form is comprised of tabs along the top which contain different aspects of the asset such as terms of leasing etc. The area of the polygon is calculated in the database and added into the form. A specific request from Sligo County Council was to show the area measurement in hectares if the area was above 5000 meters squared to have it shown in squared meters otherwise.

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The workflow can be configured to calculate and report such things as the townland or townlands the asset was captured in via a spatial query. Adjoining streets or roads can be also calculated in this way and a report can be produced and printed with the associated planning applications.

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Other features within the workflow are links to external applications within or outside the organisation such as iDocs., the ability to upload files or images, and the ability to add notes and flag one of the notes so that it then appears as the tooltip for the asset in the map.

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Various actions can be added to the map which can directly open any workflow, for instance the image shows the ability to be able to copy an existing land parcel to one of your assets just by highlighting the land parcel and right clicking the mouse.

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Smart Client has some neat features around bookmarking, you can bookmark an area of interest, save it and then e-mail it to other users or you can share the bookmark across your organisation so it is available to all users.

Access to Smart Client can be based on a windows user login and it not only has the ability to restrict users to the application but it also has the ability to restrict windows users to Smart Client Projects, Features, Workflows and even functions within a workflow. So where one user can have the ability to edit an asset other users can be restricted from doing so within the same project or view.

In addition Smart Client can be configured to launch standalone workflows, for instance if a user wants to just add attribute data to an asset they can do so by launching a standalone workflow without having to launch the GIS application.

Overall, Smart Client’s most prominent capabilities are the ability to supply a GIS application to everyone in your organisation without having to license each seat. With a shallow learning curve and the ability to provide customized workflows there is something for everyone in the audience!

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Image Source: TheSun.ie

For further information on Smart Client please feel free to contact me ckinane@imgs.ie

FME 2016 Latest & Greatest

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Author: Lauren Lucas, GIS Technician at IMGS


Hello Blog Readers!

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Lunchtime Stroll in Annecy, France

Welcome to another IMGS blog, keeping you up to date on our latest product offerings.

For this post I will be giving you a quick overview of some of my favourite snazzy updates in Safe Software’s newest release of  FME Desktop and Server 2016. These golden nuggets of information are coming straight to you, hot off the press from the partner conference in Annecy, France! My colleagues and I attended, along with Safe Software partners from all over the world, so that we could bring to you the latest and greatest of FME. Now sit back and enjoy the read, you are in safe hands….

1. FME HUB- have your say or get the answer!

As an avid FME user, I think the FME Hub is the one-stop-shop that everyone should be using. Formerly the FME Store, the FME Hub has been given a face lift and is the perfect location for you to access a plethora of free FME tools. It provides the perfect platform to share custom transformers and with a lot of free downloads available, it is a great place to broaden your FME horizons. It’s also great for privately accessing some of your own uploads, no matter where you are.

Fear not! The Hub is not all about the superusers, for any FME newbies out there, the Hub provides some great templates that will get you started. Other great tools available are Web Connections, a personal favourite of mine, which enable you to reuse connection parameters for web services that readers, writers and transformers can connect to in a secure manner.

Visit this page on the FME Hub for an introduction and see how accessing these FME tools is as easy as one, two, three.

2. FME 64 bit Memory management- got 99 problems but 64 bit ain’t one.

One of the great improvements that I learned about was the 64 bit memory management. By removing the cap on processing, the new 64 bit memory management in FME goes a long way to improving your processing speed. We heard from a fellow attendee that in one of their environments it reduced processing time from 16 minutes to just 8, so for all you big data users out there, this is something you gotta look into!

3. FME Server Licensing-additional software BE GONE!

For any of you folks our there who have had the not-so-enjoyable task of implementing a license for FME Server, the new 2016 release boasts a fabulous new licensing component which not only moves away from third party license hosting software, but also allows you to license FME Server in just TEN SECONDS….no you don’t need glasses, you read that right, ten seconds!

4. Attribute Validator- the good, the bad and the ugly.

In his talk on some of the more technical improvements in FME, Mark Stoakes, the Manager of Support at Safe Software, described the attribute validator to us as an amplifier of the good and the bad. The transformer is used to make sure that your data fits the target format data model. Validating your data before loading it into your data repository is now easier than ever, as the attribute validator pulls together the existing attribute validate tools in FME into one convenient transformer.  Some of the validation operators handled by AttributeValidator that are mentioned by Mark Stoakes in his article on the topic include:

  • Attribute type (integer, float, char, xml, json, etc.)
  • In – either a list or range – good for domain validation
  • Regular Expressions
  • Unique
  • Not Null

For any of you RegEx-perts out there you’ll be happy to know that regular expressions interface has been standardised across transformers! And you thought Christmas was months away!

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Ciara Beddy (right) and I loving the FME Conference

Check the link above to Mark’s article for a more in-depth description of this handy transformer.

 

 

 

 

5. Attribute Manager- the only manager giving you less work!

One of my favourite additions in 2016 is the attribute manager. I think the need to manage attributes is something that we can relate to and this nifty little tool goes a long way to making your life easier.

 

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Image curtosy of https://blog.rootshell.be

The attribute manager combines the functionality of multiple existing transformers into one convenient location. With this single transformer you can create, copy, remove, set, rename and reorder attributes. It effectively replaces the AttributeCreator, AttributeCopier, AttributeRemover, AttributeKeeper, ListRenamer and (as Safe have pointed out in their attribute manager sneak peak blog) given the capabilities of the AttributeCreator it also replaces the StringConcatenator, ExpressionEvaluator, AreaCalculator, AttributeRounder and more! Try saying all that in one breath!

This is something that my colleague, and esteemed FME Professional, Ciara Beddy and I are very excited about!

If you are just DYING to know more, why not view for our webinar on FME 2016 where we have covered what we consider to be the most useful updates in FME Desktop and Server.

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Ciara Beddy (Left) and I spreading the joy of FME 2016 in our webinar.

Thanks for reading!


Until next time…3ae24691c60e7f496fd95342ca8a943b


Introduction to G/Technology Fiber Optic Works

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Author: Connor Dunne, GIS Technician at IMGS.


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Image courtesy of funnypicimages.blogspot.com

Hi all, first off I would like to wish everybody a happy new year from all the staff at IMGS. So while you are taking some time off from the annual January exercise regime why not sit down and learn about one of our exciting products from Hexagon Safety & Infrastructure; G/Technology Fiber Optic Works.

Fiber Optic Works (FOW) is an advanced utility GIS that greatly enhances the complete life cycle of civil infrastructure and fiber network management.

You may have been hearing a lot about Fiber Optics and Fiber Fast broadband recently but what is it all about and why is it so exciting? The information age has created a large demand for fiber optic communication to replace old copper wire communications as it transmits information at far greater speeds. There is now a large demand for telecommunication companies to transmit telephone signals, internet communication and television signals using super-fast fiber optic networks.

With the G/Technology Fiber Optic Works platform our utility customers can manage their Fiber Optic Network from the planning stages right up to the as-built process. Fiber Optic Works addresses the inventory and connectivity of fiber, copper, equipment components, and the civil network all on one platform which means easier asset management and faster network building times.

So now on to the fun part, let’s build some Fiber network!!!

Drawing a Network

Using the standard GDesigner layout plus additional FOW tools there are number of ways to both plan and design a Fiber Optic Network. Innovative and easy to use construction aid tools allow for CAD capabilities to both design and edit network layout.

Despite popular belief the internet doesn’t just appear out of thin air; data gets fed through Fiber Optic Cables which are fed from an operator’s cabin called a Central Office. This will generally be the starting point when capturing a Fiber Optic Network.

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Image courtesy of innovactconsulting.com.au

Once we capture a Central Office then we can add a number of components to this feature. Fiber networks can be very complicated and most features are often made up of more than one component or device. FOW allows us to capture these various features for example not only can we capture the position of a central office but we can capture the layout of the cabin on the inside using detail windows. Using this detail window we can place racks and cables; this low level design is essential for engineers and network planners as it gives them great spatial awareness of each of their cabin sites. Knowing this level of design can be crucial for future planning. Below is an example of a Central Office with a detail window showing the floor plan of a cabin.

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The next stage in capturing a network will generally be to capture the cables and splice points. With its advanced editing tools we can capture the fiber cables which feed from the central office, pass through a number of enclosures where cables can be spliced and feeding into a drop point (DP) of a building. Cables are captured as linear objects in the map window, however it is not only the geographic information that is captured when these are placed as every cable carries information such as material type and fiber splice information. Validation can also be added and customised for each feature so that data capture conforms to a corporate standard. This allows for better and more efficient data capture.

However, FOW is more powerful than a simple design tool as it allows for both documentation and validation in an efficient manner. Different symbology and attribution information allow for the recording of cable distances, slack and material types etc. Having all this information in one environment is essential as it allows companies to expertly cost and make better more informed decisions on what areas they should be selling their services to. Here shows a cable with slack loop symbol. Slack information is entered into feature explorer and this attribute information is displayed in the symbol (i.e. the slack length is placed at the centre of the symbol).

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Fiber Splicing Tools

 As well as the capabilitie to draw and design a network, FOW also lets you manage and organise the splicing of fibers and port devices. The fiber feature editor tool is an intuitive application that lets you add a number of different devices to an enclosure as well as manage the splicing of fibers for various devices.

Cables can be dropped off at an enclosure and from there can be connected or spliced to a device port or to another fiber. Using both a “To” and “From” window you can pick and choose which fiber gets connected to which device or outgoing fiber. The splicing process is a simple click and drag, meaning that splicing management can be easily accomplished. Additional information such as whether a fiber is passing through or physically spliced can be added. Groove management is also possible for spliced trays and each individual fiber to fiber splice can be assigned a groove position and slot number. Again efficiency is the key here as this groove assignment process can be done automatically via FOW software. Below is the Fiber Feature Editor window. We can see that fibers that have a connection contain the splice symbolimage6.

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Fiber Feature Editor also allows the user to follow up and report on their splice connections. The splice schematic extension tool creates a schematic diagram of the splice connections; this can be printed or saved and handed out for use in the field. This information can also returned in tabular format.

Reporting

What makes FOW stand out far ahead of any other Fiber Optic Management software is its powerful reporting tools. When a network is placed there are a number of different reports that we can run for analysing a network.image8.png

With FOW it is possible to run a Fiber Path report which generates a report on the physical connections along a trace, given a starting fiber device or fiber strand. Selecting a port or strand in the Fiber Path report will display the different paths from a feature and if the feature has geometry, it will display the path in a highlighted colour. This is a quick and easy method for analysing a nodes starting point.

It is also possible to run a report on the usage of a Fiber device or strand. This type of report allows a user to know very quickly what strands or ports have a light source (i.e. if it connected all the way from a starting point) and whether or not the port is terminated. As well as reporting on a fiber/ports usage, you can also generate a report that will tell you the closest available service within a specified distance. These reports are key to the planning and day to day tasks in Fiber Optics. All of these reports can be exported to Microsoft Excel® through the click of a mouse.

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The final report tool that we can look at is a Fiber Splice Report which essentially produces a Microsft Excel® spreadsheet of all the spliced fibers and device ports. This report displays fiber strand names and colours which can be essential tool for planning as an engineer working can be given a clear visual aid of the splices to make in the field.

 

Thanks for reading.

 

FME Tips: Styling your Data for AutoCAD

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Author: Lauren Lucas, GIS Technician at IMGS


Hello Blog Readers!
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Welcome to the last blog post for 2015. Thank you for following our blog so far, we hope you have enjoyed our content over the past year and we look forward to keeping you informed throughout 2016!

December’s post takes a brief look at tips and tricks for writing styled data to AutoCAD using FME. A piece of work came across my desk recently that needed FME to write styled data in AutoCAD format, so I thought why not share my experience of the process with all of our lovely readers! Here are some of the steps that I would recommend when performing this kind of data translation.

Step 1: “By failing to prepare, you are preparing to fail”- Benjamin Franklin


The main thing that I learned from the experience is the first thing that you should do is figure out what the end product needs to look like in AutoCAD. Does the dwg file need to have specific symbology? Do the features need to have specific attribution? Are there line, point or polygon features going to be in the drawing? Are labels needed? Gathering this information at the beginning will save time… and hair-loss.

A great online application for quick viewing dwg files is AutoCAD 360 viewer; FME Data Inpector does not display AutoCAD symbology. A trial version of AutoCAD may be needed to create the required symbology in AutoCAD but I’ll discuss this later. Another thing you should cross off the list early is gathering ALL of the input datasets that will be used through out the process. Make sure you have access to these path locations and databases in FME.

Step 2: Symbolise


CAD Novice Alert!

The post is aimed at FME users that are CAD novices. The following is one approach to achieve the goal but as you all know there is more than one way to skin a cat*.skin-a-cat

*no animals were harmed in the making of this blog!

If by Christmas Miracle you are an AutoCAD superstar, please feel free to add any tips or tricks in the comments below and indeed if there is a better method out there for symbolising data in AutoCAD, please let us know!

So here’s my experience…

Once you know what the output is supposed to look like you can start to to think about how you are going to achieve it. In order to apply specific symbology to a dwg you will need a dwg template file which tells the DWGStyler transformer in FME to assign desired symbols, colour etc. Ideally the dwg file containing block styles would be obtained from the person or department that has requested the AutoCAD data which would make your life a whole lot easier- but who doesn’t love a challenge…

The template file should contain blocks (shapes in different colours, hatches etc.), the image below shows the blocks that I created in AutoCAD for my different point feature classes.

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Blocks created in AutoCAD as a dwg template file.

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You can create blocks by drawing the shapes in AutoCAD, then highlighting them and selecting the Create button under the Block section on the home tab (right). This will open a dialogue box where you can name the block and set some other parameters. When you have created all of the blocks that you need you can save the dwg file and use it as your template file in FME.

Step 3: Get your FME on!


You are now fully prepared to start with your FME workspace. Add the necessary readers for your inputs and set up your workspace to manipulate your data as desired. I would recommend that you do any heavy processing on your data in a seperate workspace, using the output of your first workflow as the input for a second workflow that will encompass your dwg styling. This will help with processing time, paramount in the testing phase, there’s nothing worse than playing the waiting game when you are only testing workflows! Another tip here is to use the “max features to read” parameter on the reader when testing, it’ll help you to establish your process faster by cutting down the time it takes to test transformers in your workflow.

3.1 Attribution

All other transformers in your styling workspace should be added to your data before you add styling or attribution. If the output needs attribution, you need to adjust some of the parameters for your dwg writer. AutoCAD doesn’t support attribution in the same way a GIS Application like GeoMedia would. When writing to dwg, you need to set the attribute output parameter to extended entity data. If you already have your writer set up you can change this setting in the navigator window under the writer parameters. Don’t forget to make sure that you have the desired attributes in the writer, they can be copied from whatever transformer or feature type that you desire so that they appear in AutoCAD. You cannot view attributes for line data in AutoCAD-in my case a single label was sufficient for line data.

3.2 Labels

If you want to create labels in your dwg, use a Label Point Replacer transformer. Unless you want to replace the geometry, make sure that you create an extra connection from your last transformer to the writer to place the Label Point Replacer on, as shown in the image below.You can also use an offsetter transformer if you don’t want your labels on top of the geometry.

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Creating a separate connection for labels so as not to replace geometry.

 

Step 4: Styling for your dwg


By using the dwg template that we spoke about earlier on, you can style your geometry using the DWGStyler transformer.


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Simply select the path to your template file in the template file space and check the box for Block/Lines/Areas/Text as needed. You can use the “…” buttons to specify the name of the block or line that you created in the template file in AutoCAD. You may need to run your workspace and do this a couple of times, checking your data in AutoCAD as you go along to make sure the output is as desired. Here’s how mine turned out.Capture5


 

Thanks for reading!

Merry Christmas and a Happy New Year from all the team here at IMGS.

Spatial Modelling of Open Source Satellite Imagery for Ireland

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Author: Lauren Lucas, GIS Technician at IMGS.


Hello Blog Readers!

Welcome to this month’s blog post on spatial modelling of satellite imagery for Ireland. This blog will provide an example of how you can work with open source imagery in ERDAS IMAGINE software and use the analysis across multiple applications.


ar129476228860485WOA! HOLD UP!

Have you seen our blog post on Finding Open Source Imagery in Ireland???? Check it out to get some background info on this month’s Blog.


How can you process and analyse Spatial Imagery?

For this blog, I will be using ERDAS IMAGINE software to process and anayse the imagery. I am going to show you an example of how you can use free data from USGS to analyse vegetation health in an urban area using this software. ERDAS IMAGINE software is a versatile and comprehensive application that combines geospatial image processing, GIS tools, remote sensing, photogrammetry, LiDAR analysis and radar processing in one solution. A major difference between a software like this and a standard GIS is that ERDAS IMAGINE has advanced capabilities in processing and analysing satellite imagery. It allows the user to work with various bands recorded or analyse each pixel value, capabilities which cannot be found in a generic GIS. As mentioned above, it also has some tools that make it easy to build spatial modelling workflows that can be used time and time again.

To give you an idea of some simple analysis that you can do with this software, I have added some screen shots further on in the post of an sample spatial model workflow created using the Spatial Modeller tool in ERDAS IMAGINE, but first let’s take a quick look at the model description.

The workflow analyses Dublin City Council’s administration area for change in vegetation between 2013 and 2015. This is useful for monitoring green space and establishing a growth norm over time for a particular season, place or crop.

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Landsat 8 Dublin City Council Admin Area , 2013(LEFT) & 2015 (RIGHT) in ERDAS IMAGINE.

The model is composed of three main sections:

  1. A Normalised Difference Vegetation Index (NDVI) which establishes vegetation health.
  2. A categorisation section to select classes of the NDVI output that reflect areas of interest.
  3. A change detection section to compare an image of the same area taken at a later date.
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Breakdown of model created in ERDAS IMAGINE’s spatial modeller.


Image 2.2.2Model Section 1: What is an NDVI Anyway?

It is a measure of photosynthetic activity, made possible by the reflective properties of vegetation. These reflections are measured by satellites on a pixel by pixel basis, giving an indication of the “greenness” or health of the vegetation.

Model Section 2: Categorisation

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NDVI output range classification

As a result of the NDVI, the output for each pixel in the image will be a value between -1.0 to +1.0 where lower values are indicative of little or no photosynthetic activity (poorly vegetated areas or poor vegetation health). To make the result more meaningful we can categorise the output into classes which will help to show us the areas that we are interested in. The classes that I have created in the model are based on the following table which defines three classes of interest.

Model Section 3: Change Detection

Now bare with me, we’re going to get a little maths-y, but I promise there’s no long division!

The change detection section of the model takes the two georeferenced images and subtracts the value of each pixel in one image from the corresponding pixel in the second image. If the result of the subtraction is greater than zero, the pixel is assigned a value of one. If the result is zero (i.e. there is no change between the pixels), the pixel is assigned a value of zero. The output image shows pixels in white (value of one) for areas where the software has detected a change in the NDVI output between 2013 and 2015.

The Outputs: Two Categorised NDVI images, one for 2013 and one for 2015, and a vegetation change detection (2013 to 2015)image.

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Output images of model: 2013 Categorised NDVI (top), 2015 Categorised NDVI (bottom) & Change Detection (middle).


Now what?

Once you have identified the area of change, you can use ERDAS IMAGINE to analyse why it might be different and even export to other applications to view the data. For example, I exported the change detection output of the model to a shape file and then added that shape file to Google Earth via ERDAS IMAGINE’s Google Earth tools.

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Vectorised output in Google Earth.

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Google Earth Comparison 2013 (LEFT) & 2014 (RIGHT) using the Google Earth time slider.

Once I had identified the location of change on Google Earth, I could use the road network data within Google Earth to identify a street name close to the area of change. I could then go to Dublin City Council’s Location Publisher, an online application with powerful interactive maps allowing the user to search for various items including planning data. I was able to use the street name that I had identified in Google Earth to find out details about the planning application and links to further details from Dublin City Council’s planning records.

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Searching for street in Dublin City Council Location Publisher to find the planning record details.


If you are interested to see more on Spatial Modeller, we have a webinar that uses this tool to analyse vector and raster data in order to identify optimum areas for residential development in county Wicklow. Please see our website http://www.imgs.ie/webinars  for more.

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Automate Residential Development Planning with Spatial Modeler. Webinar available at http://www.imgs.ie/webinars.


Need some more answers?

imagexFeel free to contact us via our website if you have any questions or would like to know more about ERDAS IMAGINE or Location Publisher.