sub foot with MM CE
Posted By J. T. Strickland on 9/1/2005 at 11:08 PM

I did an observation on a PK nail outside the office that's tied to a HARN network after twigging the projection file for the IRTF>NAD83 shift. Twenty second averaging observation, WAAS DGPS only, no external antenna, just holding it best I could over the nail.

The single freq Ashtech Solutions coords I have are:
N 1 868 369.53
E 1 165 089.96

Mobile Mapper says after 20 seconds:
N 1 868 370.18
E 1 165 089.62

That's 0.73'. I'm really disappointed, I was expecting within a couple millimeters :-). Actually, that's close to what I was expecting. That's about what it's been off by the twigging in the projection file.

I should have an external antenna cable and other accessories tomorrow. I expect the external antenna will give even tighter results. The elevations, or height above ellipsoid, are pretty tight, also. Who needs post processing for mapping any closer than this?

ESRI is supposed to take care of the shift in the next release of ArcGIS 9.2 and the next release of ArcPad, I suppose 6.4, so we won't have to play with the projection files.


Re: sub foot with MM CE
Posted By John Francis on 9/1/2005 at 11:38 PM

What kind of skies(and sat coverage) did you have?


Terry
Posted By J.D. Billings on 9/2/2005 at 12:10 AM

what procedure did you use to determine the shift parameters?

glad to see it's working.

jd



Re: sub foot with MM CE
Posted By stevie kochaver on 9/2/2005 at 6:50 AM

How did you store and retreive your coords, and, can I put a waypoint in to navigate to?


Re: sub foot with MM CE
Posted By J. T. Strickland on 9/2/2005 at 7:33 AM

John: It wasn't under canopy. It also wasn't a perfect site. In small town, buildings, under power line, power pole to the south. The PDOP was about 2 to 3. I don't remember how many birds, but definately not a full flock.

JD: I wound up using the shift based on the NGS HDDP(?) program using lat/lon at my house. The shift was about 2.3' south, 1.9' east. I also compared a couple of CORS stations (50 miles +/- away), and the shift was about the same, within a couple of tenths both ways. The twigged difference was about what the coords were showing "off" before.

Stevie: I stored it as a 2d point in
Arcpad on a layer (shapefie) that I imported from global mapper. You can store a point in arcpad also by manually typing in the coords, and do a 'go to' based on select, find, or or advanced select. Arcpad takes some playing around with to get used to. It's not as simple as a waypoint in a map330, but it's also a lot more powerful. I recommend going through the tutorials, and reading the manual. I still haven't finished all of the manual, but I'm comfortable enough with it to play with. I should finish the manual this weekend.