OpenStreetMap

My Experience, Accuracy

Posted by WillSlavin on 19 March 2014 in English (English)

OpenStreetMap relies on constant peer review, but what if nobody does a second check? Although I took care to mark my field map as accurately as possible, I realized as I was recording my features to OSM that there is a great deal of room for error. My field map differs from OSM both in scale and degree of generalization. Many of the points I added have a margin of error of at least five feet.

I was not able to connect with a fellow student while doing my survey. This is why I chose to record multiple types of features. To increase the accuracy of my additions, I could do a second survey and make notations on an OSM printout. I would have done this if some of my additons were made before today (2/18).

I have done some mapping in the field with a gps and with survey equipment. This is different because you can't be sure your features will be accurate.

I did have an Idea that would certainly increase accuracy. I know that there are apps which take gps data from a cell phone, and I think some of them may output to a shapefile format. I think that using this sort of app along with OSM could be really cool. I could take a point with my phone, take a picture of the point I just took, and upload it to arcmap as a reference. The downside of this is that you would have to have a georefferenced image or some way of matching the shapefile with the campus.

I would like to develop a web map that could take a point (in the projection that OSM uses) and saves it to a shapefile, or better yet, a format which OSM could somehow understand. I have a basic idea of the structure, but I don't know if OSM has that sort of capability... yet.

p.s. Damon and Stephanie - I could'nt figure out how to link images in time so I'll email my fieldmap.

Comment from DaCor on 19 March 2014 at 04:28

You SFSU folks should take a look at some of the existing apps available for doing OSM surveys

On Android there's OSMTracker, KeypadMapper, OSMTracker, Vespucci etc

For ios there is PushPin and others

Using these can really speed up your data gathering with the added benefit of data going directly into OSM (PushPin & Vespucci) or allowing you to load your gathered data directly into Jose (OSMTracker & OSMpad)

Btw, I'm loving the work you folks are doing, the campus is looking better by the day

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Comment from DaCor on 19 March 2014 at 04:29

That should say Josm, damn auto-correct

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Comment from mhenson on 20 March 2014 at 14:36

I would like to add OSMAND to the Android list. https://play.google.com/store/apps/details?id=net.osmand

OSMAND main purpose is navigation, but I have found it very used to map POI and Bugs. The POIs and Bugs are directly uploaded to OSM. It will also allow you to download maps (OSM and Bing aerial) to your phone, so your cell data can be off while mapping. Once home, you can use the wifi to upload all the POI and Bugs. (I currently use an old smart phone that is not activated and strap it to my bicycle so I can map other neighborhoods that are to far for a walk)

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Comment from pnorman on 23 March 2014 at 06:11

You're not going to get an accuracy of better than 5 feet out of a cell phone GPS. In practice, the best accuracy is from properly aligned imagery, the type city GIS departments purchase.

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