I'd like to map some streams in my area and I'm looking for best practices. They're not accessible to track using GPS so I was going to use imagery to map them. The streams are visible on some of the Bing Aerial imagery but not always, but the USGS Topographic maps are very accurate. Is it considered "ok" to use the Topo imagery to trace the streams? Are there best practices with regard to doing so?

asked 20 Aug, 15:54

mccarbc's gravatar image

accept rate: 0%

USGS topographic maps are okay to use as a source (that type of US government publication is public domain).

In my semi-arid area I use the USGS maps (selected in the JOSM "imagery" pulldown) for three things when mapping waterways:

  1. To see if the waterway is considered big enough to map (I also look at available aerial imagery). There are lots of dry gullies around here that may have a visible ephemeral water course that carries so little water so rarely that it is debatable if it counts or not. But if the USGS thought it counted then I figure that is an indication that OSM might be interested in it.

  2. To see if the waterway has a name.

  3. To roughly draw the waterway in.

I find that the USGS topo imagery layer in JOSM (which uses the older maps) to have a fair number of errors in location. So once I get the waterway drawn in per the USGS topos I then adjust it based on imagery to get a better location.

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answered 20 Aug, 16:30

n76's gravatar image

accept rate: 18%

Thanks, your answer was very helpful. I plan to do as you mentioned, first map using the USGS Topo layer then adjust using the Bing imagery.

(20 Aug, 18:01) mccarbc

I think the big thing to be aware of with USGS topos (as with NHD data) is that sometimes the survey data is quite a way in the past, but as an aid in conjunction with recent imagery they are invaluable.

(21 Aug, 11:20) SK53 ♦
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question asked: 20 Aug, 15:54

question was seen: 191 times

last updated: 21 Aug, 11:20

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