Experiments in mapping new buildings

classic Classic list List threaded Threaded
5 messages Options
Reply | Threaded
Open this post in threaded view
|

Experiments in mapping new buildings

Tom Taylor-2
I've tried a couple of ways to survey in new buildings with my GPS.
Obviously, just walking around the outside won't work because of
reflections and obscuring of satellites. So first I tried sighting along
each edge while walking toward or away from the building and keeping a
track. Results were mediocre because the error was a bit high in spots.

I've gotten more satisfactory results by sighting along each edge and
collecting a single averaged waypoint on each side of the building to
let me draw a line. This takes a while -- eight points just for a
rectangular building. Cold work at -15 C. (5 degrees F.), I must say. At
the end of it, I know the estimated error at each point, and the results
seem satisfactory when I draw them out.

Maybe obvious, but for me it was lesson learned.

TomT5454

_______________________________________________
newbies mailing list
[hidden email]
http://lists.openstreetmap.org/listinfo/newbies
Reply | Threaded
Open this post in threaded view
|

Re: Experiments in mapping new buildings

St Niklaas
Hi Tom,
You also could try to do it with 2 points (lat & long secured) shooting alongside the visible sides of the building. At the map, you could work with geography to measure it out.
If you have sight on other buildings or recognisable vieuwpoints you even can draw helplines (figutively) alongside the outsides of the building and work it out the same way. But it gets tricky if the building has more the 4 corners.
Greetz
 
> I've tried a couple of ways to survey in new buildings with my GPS.
> Obviously, just walking around the outside won't work because of
> reflections and obscuring of satellites. So first I tried sighting along
> each edge while walking toward or away from the building and keeping a
> track. Results were mediocre because the error was a bit high in spots.
> _______________________________________________
> newbies mailing list
> [hidden email]
> http://lists.openstreetmap.org/listinfo/newbies


_______________________________________________
newbies mailing list
[hidden email]
http://lists.openstreetmap.org/listinfo/newbies
Reply | Threaded
Open this post in threaded view
|

Re: Experiments in mapping new buildings

ael-3
In reply to this post by Tom Taylor-2
On Sun, Jan 27, 2013 at 04:36:56PM -0500, Tom Taylor wrote:
>
> I've gotten more satisfactory results by sighting along each edge
> and collecting a single averaged waypoint on each side of the
> building to let me draw a line. This takes a while -- eight points
> just for a rectangular building. Cold work at -15 C. (5 degrees F.),
> I must say. At the end of it, I know the estimated error at each
> point, and the results seem satisfactory when I draw them out.

Don't overlook the possibility of using a (decent) compass in
conjunction with GPS. JOSM (I have recently discovered) shows
bearings when drawing ways, and a new version of Viking will
also support drawing "construction" lines along bearings.

I recently used this technique to map a new wind turbine where I
couldn't approach it directly.

I guess that you could take waypoints "aligned" with the sides of
buildings and record the bearings. That should work for isolated
places, but probably not directly of use where the builings are
crowded together.

ael


_______________________________________________
newbies mailing list
[hidden email]
http://lists.openstreetmap.org/listinfo/newbies
Reply | Threaded
Open this post in threaded view
|

Re: Experiments in mapping new buildings

St Niklaas
Hi Ael, 
> I guess that you could take waypoints "aligned" with the sides of
> buildings and record the bearings. That should work for isolated
> places, but probably not directly of use where the builings are
> crowded together.

Your working like a surveyer with the red and white sticks (jalons). Making lines visible in the open area. You also could use the same methode to map anything that s rectangular or straight for some distance and mark the turning points with your GPS.
Good Luck and Happy Vieuw
> _______________________________________________
> newbies mailing list
> [hidden email]
> http://lists.openstreetmap.org/listinfo/newbies


_______________________________________________
newbies mailing list
[hidden email]
http://lists.openstreetmap.org/listinfo/newbies
Reply | Threaded
Open this post in threaded view
|

Re: Experiments in mapping new buildings

James Ewen
In reply to this post by Tom Taylor-2
On Sun, Jan 27, 2013 at 2:36 PM, Tom Taylor <[hidden email]> wrote:

> I've gotten more satisfactory results by sighting along each edge and
> collecting a single averaged waypoint on each side of the building to let me
> draw a line. This takes a while -- eight points just for a rectangular
> building. Cold work at -15 C. (5 degrees F.), I must say. At the end of it,
> I know the estimated error at each point, and the results seem satisfactory
> when I draw them out.

Extending the sight lines off the edges of buildings also works to
reduce your angular errors.

If you are standing 100 meters away from a building edge, and sighting
along it to get lined up properly, then collecting an averaged
waypoint with an estimated error of 3 meters would give a possible
angular error of about 1.72 degrees.

If the side of the building you are sighting along is 10 meters in
length, then the error at the close end of the building would be on
the magnitude of 0.3 meters.

This is only significant for getting the angles correct. The GPS
locations can still all be shifted horizontally from where they should
be by the common error.

--
James
VE6SRV

_______________________________________________
newbies mailing list
[hidden email]
http://lists.openstreetmap.org/listinfo/newbies