I have a project in LDT that is on state plane coordinates and was started by loading a profile like always, when we check the Lat/Long, the Lat is off by over a degree and the Long is off by over 8 degrees. The autocad and project drawing coordinates are the same (0,0) for both and North is straight up. The zone has been checked and is correct, the N/E coordinates match the published data sheets, but the Lat/Long don’t. This may not be a bid deal for a lot of surveyors that don’t need Lat/Long, but the bulk of my work now is doing cell tower sites and preparing 1A’s and 2C’s and would hate to have to start checking everything with corpscon. We opened other project drawings and they are still correct. Does anyone have any suggestions as to what can cause this?
TIA.
You say you've rechecked the zone, but have you rechecked NAD27 vs NAD83 and feet vs meters?
Yes, NAD 83 in feet, NAD 27 around here is about 100' different.
Any chance that your coordinates are N,E,Z vs. E,N,Z or that the Lat/Lon function in LDD is expecting input in a different format than it is getting? Ran into this awhile back where the batch convert for Corpscon was expecting E,N,Z while the single point conversion allowed N,E,Z. The difference caused another poster quite a bit of head scratching.
Edit: Also even though you've got the correct zone and unit set in LDD, if the coordinate file was in state plane coordinates and collected with NAD27 rather than NAD83 the difference in the false northings and eastings could cause a significant error. Tennessee for example in NAD27 uses a false northing of 100,000 feet and a false easting of 2,000,000 feet where as NAD83 uses false northing of 0 meters and a false easting of 600,000 meters. Once you do the conversion from meters to feet there's a difference of 31,500 feet in the easting and 100,000 feet in the northing.
Drop a rectified aerial in the drawing and see where it lands...
If you're using ACAD12, type in goog to see where google maps puts you.
The survey was started from two published monuments on NAD83 in feet and the water tank that we are surveying has has published coordinates on it. The county GIS and Google match the published Lat/Long. There has to a setting in this project that has changed because other projects still list the correct Lat?Long, I just have not been able to figure what it is. I am glad that it is over 8 degrees, it make it easier to see that something is wrong. I am posting this for information for others to be aware of as much for me trying to out what is wrong. What if if just gets off by a little bit?
Decimal degrees? instead of D-M-S?
If your State Plane projection is Transverse Mercator, I would suspect you're in the wrong zone - (incorrect Central Meridian) and the False Northing might be different, too.
> The zone has been checked and is correct, the N/E coordinates match the published data sheets, but the Lat/Long don’t.
Could be that you have the correct zone in LDT but whoever calc'd the coordinates you imported didn't.
The coordinates came straight off the NGS data sheets for the monuments that we came off of.