I've received a 1983 dataset from a California agency. The coordinate system is nothing I've ever seen before. Attributes say "North_GPS" and "West_GPS", and value pair examples are all similar to (-33471.539,159239.375) I've tried several different decimal meters coordinate systems, but nothing works. I know the actual locations should be on the east slope of the Sierras, so I'd expect to get coordinates in UTM NAD83 Zone 10 or UTM NAD27 Zone10. My data source agency has no idea. These pairs are especially weird since there is a "westing" instead of an "easting". Anyone have any ideas of what system these use?
does the agency use something other than UTM... they aren't decimal degrees, but maybe some projection that has a larger east west extent than UTM .... Albers? in the states, we use Lambert conformal conic in Canada for such situations
Dan, thanks for your reply. No, they only use UTM now (CDFW). I am using ESRI ArcMap (of course) and have tried a dozen or so different options, though not Albers. So if this isn't in decimal meters what is it? It isn't degrees.
if it were UTM you wouldn't have any negative values since the central meridian is designed (500,000m) with that in mind. Lambert CC (Canada) specifies a different central meridian and assigns a value of 0 to it so negative numbers suggest to me that it is some kind of wider in the east west direction with a value of 0 m or 0 ft assigned to it, so that locations west of it will be negative and values east positive. the "northing" to use the term loosely, is a whole different ball game. That is why I ased if the organization used some other coordinate system the -33 threw me off since initially I thought it might be a latitude in the southern hemisphere....just screwed up, ditto for the 159... So your guess is as good as mine. but it isn't longitude and latitude and it isn't UTM
I second the suggestion by Curtis Price California Teale Albers is a very popular coordinate reference system here in California, particularly with the State.
Several years ago when ESRI added Teale Albers to ArcMap as one of the listed standard projections, there was much celebrating.
Chris Donohue, GISP
Follow on info for the original poster:
If you want California data that is in native Teale Albers NAD83 to match against your data, you can download some from CAL-Atlas:
For example, there is a county boundary shapefile in Teale Albers (cnty24k09):
Projected Coordinate System: NAD_1983_California_Teale_Albers
Linear Unit: Meter
Things to note:
- Negative values will be present in some areas and that is OK.
- Units are in meters.
Also, there is a Teale Albers NAD27 flavor out there, so keep an eye out for that.
Chris Donohue, GISP
I also think it's Teale Albers. The question is whether it's the NAD27 or NAD83 version. The NAD27 version puts the data near the border of Sierra and Nevada counties. It would have to be a meter-based version too. The NAD83 feet version lands the data outside the state.
easting / x = -33471.539
northing / y = 159239.375