GIS/CAD survey software

[Andy Clark]

One for the IT savvy out there........

 

I'm interested to hear of how folks who survey, join the dots between GIS based and/or CAD based surveys.

 

We do lots of general tree stock surveys, all of which are GIS based with trees plotted straight onto the O/S Mastermap using an Arcpad front end for data capture, and then manipulated on desktop using GIS.

 

We also do a lot of 5837 planning surveys, but these tend to be onto .dwg topo plans or architect drawings using CAD.

 

I'm of the impression that the ONLY way to make CAD plans work on a GIS system is if the CAD file is geo-referenced...... is this right?

 

Or does anyone know of another way to link the two?

[daltontrees]

One for the IT savvy out there........

 

I'm interested to hear of how folks who survey, join the dots between GIS based and/or CAD based surveys.

 

We do lots of general tree stock surveys, all of which are GIS based with trees plotted straight onto the O/S Mastermap using an Arcpad front end for data capture, and then manipulated on desktop using GIS.

 

We also do a lot of 5837 planning surveys, but these tend to be onto .dwg topo plans or architect drawings using CAD.

 

I'm of the impression that the ONLY way to make CAD plans work on a GIS system is if the CAD file is geo-referenced...... is this right?

 

Or does anyone know of another way to link the two?

 

I'm borderline clueless about how it all works, but I think that fundamentally the plan HAS to be geo-referenced.

[10 Bears]

Yes you are correct Andy. Georeferencing is a simple term meaning to tie one part of a map, say an aerial image or a raster background map to known coordinates such as GPS points taken at specific features on site.

 

You should take your vectors (GPS points) at recognisable places that you would find on your base map (so scale of the base map is important here) such as corners of buildings or walls etc. and reasonably spread about your site. You will then be able to find these reference points on your map and drape the GPS coordinates over them, thereby linking the two.

 

You don't have to have a fully projected CAD topo, but you do have to have a way of matching the base map, with GPS points and the vector map (CAD) otherwise you wont know where each is in time and space. In most GIS, you can write an attributes table to tell the GIS where a particular reference point is (such as the wall corner), and again relate that to your base map. The vector map will then be projected over the top of the raster with minimal distortion if you have enough reference points.

 

There are other methods to achieve this though, such as using robotic surveying or terrestrial laser scanners, but I think they are probably a bit much for your needs!

[Nick Burke]

I'll look into exactly what you need to do but as all have said yes needs geo reference for points. AutoCAD can convert shape files to DXF/DWG files.