I'm doing a lot of mapping in rural Alaska and am looking for a way to set the proper offset for the maps I use in JOSM. There are no GPS traces or roads in my areas of interest and the various map overlays I use (primarily Digital Globe Premium and Standard, ESRI, and USGS Topos), do not align perfectly with one another. Without some fixed point or points to use as an alignment aid, the objects I'm adding could be off by a significant distance. The problem then, is how to position one of those overlay maps correctly so that I can use it to align the others.

The USGS Topo overlay is crucial to my work for adding names to geographic features. They also contain many "named" benchmarks and VABM (Vertical Angle BenchMark) points. Is there any place on the Internet that has a list of those benchmarks that contains their lat/lon coordinates? And if so, are the coordinates accurate enough to use as a geo-referencing point? If I had one or two points with accurate positions in a given area, I could align the Topo with them and then use the adjust the offset of the other maps to match the Topo.

Maybe there is some other way to accomplish this? Any feedback or suggestions would be appreciated.

Thanks for your help.


PS: There is no way I can get to the areas I'm mapping to check some well-known points or do GPS averaging. These areas are remote in every sense of the word. The only way into the regions is via an expensive bush plane flight.

asked 26 Feb, 12:19

AlaskaDave's gravatar image

accept rate: 10%

edited 26 Feb, 12:34

Will this work for you: https://www.ngs.noaa.gov/NGSDataExplorer/

I zoomed into one of the areas I hike at where I know there are bench marks. I was able to get a list of the marks there and clicking on one of those got the information about it including the NAD83 lat/lon.

permanent link

answered 26 Feb, 17:07

stf's gravatar image

accept rate: 19%

That's an excellent resource. I will fool around with it for a while and let you know how it works. FYI, on one of the data sheets I pulled up it says the point was derived from a USGS Topo, which would make it useless to help position same topo. But on others the lat/lon coordinates appear to be very precise (e.g. 59 47 14.35033, -151 05 08.79052) and have been field checked. Those points could prove to be very useful.

Thanks very much.

(27 Feb, 02:01) AlaskaDave

The site is a good one and has helped me align the USGS topo layer with ESRI and DigitalGlobe imagery. It's a tedious process but better than what I had before, which was nothing.

Thanks again for your answer.

(09 Mar, 22:38) AlaskaDave
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question asked: 26 Feb, 12:19

question was seen: 126 times

last updated: 09 Mar, 22:38

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