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Discussion: Uploading OCAD maps to Avenza

in: Orienteering; General

Jan 9, 2021 3:47 PM # 
Hammer:
Does anybody on this forum have experience with uploading georeferenced maps to Avenza?

I have produced a map of a local nordic skiing club but I am having georeferencing issues post upload to Avenza. The map is lidar based as is georeferenced and I've had success using it with MapRunF. When fieldwork GPS tracks are imported to OCAD they are perfectly georeferenced.

But when I upload the PDF to Avenza it alters the georeferencing. The middle of the map aligns perfectly but the West-East shrinks while North-South is expanded/stretched. I've reached out to Avenza twice but haven't received any response (perhaps because my map is free). I

If others have had this issue or perhaps could assist with trouble shooting it would be greatly appreciated.

A PDF of the map is located here:
http://www.challengetheshield.ca/gnoac.html

Thanks!
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Jan 9, 2021 3:57 PM # 
Terje Mathisen:
From the error description I wonder if Avenza only supports Google Maps style "Web Mercator"?

This is a bastard projection which unfortunately has become pretty much the world standard for online maps. You can probably use GDAL to compress/stretch your UTM projection map images to fit this format.
Jan 9, 2021 5:55 PM # 
CraigW:
I have imported two maps into Avenza with excellent results. I exported from OCAD 2018 into (geo)tiff files. I know OCAD can now export geo PDF, but have not tried them. The maps are UTM/WGS 84 Zone 18N.
Jan 9, 2021 10:38 PM # 
iriharding:
I have used the export to pdf function of Ocad 2020 with georeferenced files and uploaded to Avenza and used Avenza map in the field with no problems.
Jan 9, 2021 10:47 PM # 
Hammer:
Not sure what I’m doing wrong. Back to the drawing board
Jan 9, 2021 10:56 PM # 
RickD:
I haven't uploaded anything to Avenza since January 2020, so maybe they've changed something recently. I used the same procedure as Craig's, with no problems. I.e., OCAD 2018, export as geotiff, UTM WGS 84.When I look at the info in Avenza for this map, it suggests the projection is transverse mercator.
Jan 9, 2021 11:57 PM # 
haywoodkb:
I have some maps on Avenza as GeoTIFFs exported from Global Mapper. The Avenza instructions list a dozen different projections that work, but my only success was with Mercator.
Jan 10, 2021 5:17 PM # 
bchubb:
I opened your pdf in Global Mapper and it opened it as Geographic (Lat Long). I don't think it does that by default. Is it possible your original basemap is unprojected? I know that NTS map sheets an be downloaded as UTM or Unprojected.
Jan 10, 2021 10:47 PM # 
Hammer:
Thanks Brian I think that is the issue. Basemap is from original lidar.
Jan 11, 2021 8:56 AM # 
Terje Mathisen:
The quickest/easiest verification that georef info is OK is to export (a part of) the map as a Google Earth KMZ raster and click on it to check that it ends up in the proper location.
Jan 13, 2021 11:44 PM # 
Hammer:
Thanks everyone for the help and advice. I think the version I have under review at Avenza is going to work. Testing with the temporary link provided suggests all is good. Avenza did eventually get back to me but AP had the issue solved before them. Gotta love the orienteering community. Cheers.

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