topic Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West in Data Management Questions

Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Tue, 08 Mar 2016 22:08:27 GMT

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?

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

DanPatterson_Retired — Tue, 08 Mar 2016 22:17:53 GMT

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

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Tue, 08 Mar 2016 22:26:25 GMT

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.

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

DanPatterson_Retired — Tue, 08 Mar 2016 22:36:28 GMT

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

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Tue, 08 Mar 2016 22:39:00 GMT

Thanks again Dan. I'll try Lambert and Albers when I get back to work tomorrow. I really appreciate your replies. Jean

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

curtvprice — Wed, 09 Mar 2016 06:19:29 GMT

Teale Albers, perhaps?

California Teale Albers, NAD83 projection: SR-ORG Projection -- Spatial Reference

.prj files and California (Teale) Albers NAD83 - Region 3 GIS

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Wed, 09 Mar 2016 18:24:02 GMT

Hi Curtis,

Thanks--I'm going to do more experimentation when I get back to work (and to my Arc license) on Friday.

Jean

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

ChrisDonohue__GISP — Wed, 09 Mar 2016 21:12:29 GMT

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

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

ChrisDonohue__GISP — Wed, 09 Mar 2016 21:38:39 GMT

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:

CNRA Download

For example, there is a county boundary shapefile in Teale Albers (cnty24k09):

CNRA Download

Teale Albers:

Projected Coordinate System: NAD_1983_California_Teale_Albers

Projection: Albers

False_Easting: 0.00000000

False_Northing: -4000000.00000000

Central_Meridian: -120.00000000

Standard_Parallel_1: 34.00000000

Standard_Parallel_2: 40.50000000

Latitude_Of_Origin: 0.00000000

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

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

MelitaKennedy — Thu, 10 Mar 2016 00:16:51 GMT

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.

That's assuming:

easting / x = -33471.539

northing / y = 159239.375

Melita

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

BruceNielsen — Thu, 10 Mar 2016 17:40:53 GMT

Have you tried each of CA's State Plane projections?

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

MelitaKennedy — Fri, 11 Mar 2016 19:35:33 GMT

Unfortunately, you're not going to get negative coordinates using a state plane zone, unless the data is well outside the zone's defined area of use. The state plane zones (and UTM) were designed when doing calculations by hand or maybe on a desktop calculator. You didn't want to have to deal with both positive and negative values.

Melita

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Fri, 11 Mar 2016 22:12:09 GMT

Thanks everyone. I did try everything with CA prefix, including all of the State Plane systems. The closest possibility turned out to be Projected State Systems NAD_1983_2011_California_Teale_Albers. However, the positions were still wrong. These are sample sites on CA trout streams, and the points ended up about 127 miles southwest of the streams they were taken from. I tried translating the entire group of sites northwest to see if they would line up on the correct streams, but no. So I think I have garbage data. I'm going to have to estimate from marks on poor quality paper maps. I do appreciate all of the feedback I received; it was very helpful and I learned a lot.

Re: Strange California Coordinates (-21678.911, 157257.553) marked GPS_North, GPS_West

JeanBarney — Fri, 11 Mar 2016 22:12:59 GMT

Uh--I meant 127 miles southeast, not southwest.