3

I have a set of 4 control points used for H and V localization. There is a base point located far to the SW of the property. I did not create this myself, but took it off of an existing Pocket 3-D project from a past employee. I didn't know any other way to find a base point b/c the company is too far out in the country for existing survey marks. The data from points and lines I create in this localization all end up inside the control points where they should be as I set up the base station over the control points 1-4, and the base control point only has N 5000, E 5000, and Z 1000, so no way to figure out where it really is. However, when I got on the computer version on the program, and looked at the list of control points, it shows the WGS84 locations for the control points. The base's WGS84 location in actually inside the control points, so now I'm very confused. I can't figure out how to get WGS84 coordinates for the points, polylines, ect, and have been trying to shoot it though the program's coordinate calculator, getting results saying I'm in eastern Colorado, ect. I'm in North central Kansas, so that's not even close.

I understand that I may need to just start over, and if I do that, I'll need some serious survey advice. I'm an ArcGIS user, stuck doing my first real taste of surveying in the context of construction grade, sub-centimeter level, products (Topcon, Pocket 3-D, 3D Office). I have no training in this really, and there's no one at this company for me to talk to, as I'm basically my own department. Please help! I got in a bit deeper than I expected!

screen shot

BASE is N 5000', E 5000', E 1000' * N38.561866674', W99.212131227', H 2081.0391' CP 1 is N 7443.5450', E 6320.5000', E 2065.9120' * N38.561000637', W99.214876310', H 2089.3173' CP 2 is N 10039.8030', E 6336.8390', E 2064.4450' * N38.563566563', W99.214856097', H 2087.8405' CP 3 is N 10040.2260', E 8942.3830', E 2080.0470' * N38.563567238', W99.211558647', H 2103.4836' CP 4 is N 7445.9530', E 8922.2990', E 2032.7590' * N38.561003304', W99.211584006', E 2056.1248'

the other points in the screen shot were used to get closer to the area I was surveying with the base receiver, but were not used for Horizontal or Vertical localization. Also, the error values on the control points are now higher than they were when I started, is that normal?

Localization Screenshot

This is what's coming up on the program. It sits where it should on Google Earth, maybe slightly skewed, but the lat and long is different from what is in your picture from QGIS. enter image description here

  • An alternate resource to GIS.SE would be surveyorconnect.com – Chris W Oct 23 '14 at 23:22
  • thanks, that was a really helpful suggestion. I found a thread there on localization. – Rachael63 Oct 24 '14 at 13:16
1

I don't know the software you use, but I could get the data into QGIS:

enter image description here

The corner points and the one from the second screenshot seem to be correct in North Kansas, and correspond to real estate borders in Google satellite imagery. Two sides are made up of streets that are in OSM maps as well. As you found out, the base point WGS84 coordinates are wrong (they are inside the area and not to the SW of it).

But it is possible to recreate the base point form the other four, and make a local grid in oblique stereographic around it. I actually did it in UTM 14N with coordinates recalculated in meters, and then did some statistics to get it fitting. The corner points are less than half a feet off.

The proj definition of my projection is:

+proj=sterea +lon_0=-99.3681888 +lat_0=38.92940435  +k_0=1 +x_0=1524.003045 +y_0=1524.003045 +ellps=WGS84 +units=us-ft +no_defs

Please note that all your coordinates are in feet, or degree-minute-seconds, while QGIS and GDAL expect decimal degrees. False Easting and Northing are in meters, regardless of the projection units.

  • So basically what you're saying is that I could go to the field controller and create a new grid for it and just set up the base receiver at one of the four control points, and create a new base point somewhere (inside or outside??) to use instead? – Rachael63 Oct 24 '14 at 20:24
  • Those four corner points seem to fit to each other, so you might take the lower left as new base. I still wonder how the old base got wrong, and how yo ended up in Colorado. The Z coordinate of 1000 feet for the base also does not make sense, if all other points are above 2000 ft. – AndreJ Oct 25 '14 at 5:22
  • I think that whoever set that up initially went with the example from the manual... I believe it said to go with 5000, 5000, 1000 for some reason. I end up in Colorado when I try to use the coordinate calculator to turn localized coordinates into WGS84 for Google Maps. I think my logic is off or I screwed up something with the Geoid, Projection or datum. – Rachael63 Oct 28 '14 at 12:17
  • Since the corner points are good, try to set a new base point and start from there. – AndreJ Oct 28 '14 at 12:29
  • ok. I got it to load up correctly in a related program, but the linework I did inside the localization is shot off clear out of it. I can't start over yet, unfortunately, the roving receiver fell over and wouldn't turn back on so it got sent out for repair. I'm just trying to figure out the PC software's representation now. – Rachael63 Oct 28 '14 at 12:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.