Georef an image?

[Benson Shaw]

OK, next question on GIS. I need to georeference a scan of a neighborhood map.

In ArcGIS and other GIS software (I don't own), an image file (eg a satellite photo or scan of a paper map or drawing) can be accurately georeferenced by assigning known lat/long values to 4 or more feature points on the image. The known values can be obtained from corresponding points on other GIS sources such as Google Earth, City/County GIS shape files, etc. The software distorts the image so that those points on the image coincide with the known points, and assigns virtual location to the image so that accurate point location data can be retrieved from features in the image.

Can VWX georef’ an image to this standard? Or do I need dedicated GIS software? I know vwx can squish a square onto a projection, but that's not quite same as stretching and compressing between several known points to make everything line up.

Thanks for relating any experience.

-B

Edited December 16, 2015 by Benson Shaw

[Art V]

No Vectorworks cannot do this, you will need a dedicated GIS program.

A free GIS program that can do this is QGIS, a cheaper alternative to ArcGIS is Global Mapper (Windows only) which can also georeference images.

If you are going to work on GIS I strongly suggest to get at least QGIS or a good but not expensive alternative to ArcGIS such as e.g. Global Mapper or other programs. This to verify the import/export went correctly.

As much as I like Vectorworks, given the past issues I recommend for now to check against another GIS capable program to see if the import went well. If so there should be no further problems if you leave the georeferencing alone from then on in the document. Upon first export I'd also check the output. If that is ok too then future imports/exports into/from the document should be ok as long as the georeferencing of the document has not been changed.

Though I'd do additional checks if you are going to import from one a different CRS than specified in your VW document.

Currently the list of datums (though not all items listed as datums are real datums from a technical perspective) is limited so conversions may not always be correct.

Which is why I'd like to see the EPSG catalog to be implemented in a future version of Vectorworks, as this may alleviate quite a few conversion concerns.

Edited December 20, 2015 by Art V

[Benson Shaw]

Thanks, again Art

I delved into this because I need to georeference that scan of an aerial photo and wondered if vwx could transform it to fit the GIS street grid.

I did a self guided crash course in QGIS (Open source, Free, Very comprehensive!) and managed the task quite well with help of a few of the many online tutorials and examples.

Vectorworks is providing heaps of capability and interoperability with other software including the GIS genre. I'm pretty impressed it got me as far as it did, so I'm not complaining.

Transforming/georeferencing bitmaps would be a great addition so that's a wish.

-B