Tag Archive for 'ArcGIS'

It must be the heat wave, otherwise I can’t explain why today I had to accomplish some very unusual, not to say weird, GIS tasks.

One part of our work here is to collect and synchronize data from various regional or federal institutions and produce a national view of certain spatial planning related topics. The bandwidth of responds to our data requests is pretty broad: it reaches from colorful word or excel tables to every digital image format (particularly when it comes to geographic data and maps) you can imagine. GIS compatible data is unfortunately the big exception. The worst, and in the year 2006 still existing, answer you can get is “I send you the data by fax, ok?”.

Adobe Illustrator to ArcMap

During the last days we received some maps done in Adobe Illustrator. For some reasons GIS was ignored and the whole mapping was done exclusively by vector graphic editing. For print-only maps it was ok and we could add the delivered Illustrator files to our graphic outputs. But we needed the data in our Mapserver too.

The workaround I found was to export the features (points and polygons) from Adobe Illustrator to AutoCAD Interchange file (dxf) and then import this AutoCAD files into ArcMap. The import/export allows you to take over the layer information (the graphic elements were organized and grouped into different layers) as attribute like in any other dxf. Completely missing is of course a coordinate system. Once I had all the elements loaded into ArcMap I used the Spatial Adjustment tools to shift the former graphic elements to their right geographic location within my chosen coordinate system. To successfully complete the spatial adjustment you need to know the exact location (e.g. some graphic lines represent a known street network) of at least a few graphic features.
Of course you won’t achieve sub-meter accuracy by this method, but for a first rough import step it was ok. Further spatial adjustments along with other editing steps (such as adding attributes) need to be done on the imported data in order to ensure a certain quality level.

Coordinate system?

Another data set which was meant to be added to the Illustrator data was stored within an Excel table. First I thought great, somebody who understands my needs: the last two columns represented coordinate pairs. Fantastic! I’ll be done in 10 minutes. After the X/Y-import the data just didn’t want to match any coordinate system I knew. Whatever projection parameter I modified, the data just slipped around on my map, always slightly off my existing data (the position of some features was known). It took me the whole morning to figure out what was wrong with the coordinate pairs: every third coordinate pair applied to another coordinate system. I’ve never seen such a data compilation before. After splitting everything up, defining the right coordinate system for each pair and putting them together again I could add this data my maps.

If today’s data struggle wasn’t enough, my PC was behaving sluggish and unmotivated all day long. Must be the heat or a signal to go home now.