Re: Missing features on 7.5 minute topo maps?
Posted: Mon Nov 05, 2018 11:59 am
GPS users should also know what base map their GPS is using. If the GPS gets trail locations from a USGS 7.5 minute map, it also will contain the same errors. Maps are approximations of terrain, better than nothing but not perfect. Dry streams and trails can often be "teased" out of satellite images with algorithms that look for linear features. This is used a lot in geologic mapping. It would take a lot of historical data to determine if some of the smaller streams are permanent. I have observed some relatively large streams in Yosemite go late season at the end of a severe drought. Intermittent streams are usually defined as those that regularly dry up in late season. One must be a bit skeptical of water sources if you do late-season backpacking.