I'm looking at the map of our local lake here in California. I'm trying to match the coordinates I find on the printed map to my GPS, so that I can enter way points into my unit. But it is using something other than standard GPS coordinates. I searched around, but I didn't find anything that resembles this coordinate system.

 

Here is one example.

 

One spot I was interested on Google map (Lexington Res in California) has GPS coordinate of about:

 

+37.19'39.80", -121. 59' 24.93"

 

On the printed map that I acquired from the local water agency who oversees this lake, the same spot is marked approximately at:

 

"48,000N, 50,000E"

 

Can someone tell me what these numbers are? I mean, why it is even E(East)?

 

Thanks!

 

 

Make sure you use the same map datum

Jeff

Make sure you use the same map datum. Google maps uses wgs84

Jeff

Back in the old days, different agencies used different coordinate systems than the now Standard, WGS84.  Some still do.  The coordinate system used for the map should be stated on the map, or should be accessible from the water agency. I suppose Google would the the best way to find out how to convert the old to the new.  Send a PM to Alpster.  He's a land surveyor, and is very conversant with the more archaic coordinate systems.

I believe those are UTM coordinates, google it, it is a simplier way than degrees, minutes and seconds IMHO. You can also find a converter on the net to convert to your prefered coordinate system.

The agency is giving you a spot which is approximite while google is giving you one down to the meter

I'm looking at the map of our local lake here in California. I'm trying to match the coordinates I find on the printed map to my GPS, so that I can enter way points into my unit. But it is using something other than standard GPS coordinates. I searched around, but I didn't find anything that resembles this coordinate system.

 

Here is one example.

 

One spot I was interested on Google map (Lexington Res in California) has GPS coordinate of about:

 

+37.19'39.80", -121. 59' 24.93"

 

On the printed map that I acquired from the local water agency who oversees this lake, the same spot is marked approximately at:

 

"48,000N, 50,000E"

 

Can someone tell me what these numbers are? I mean, why it is even E(East)?

 

Thanks!

 

The bottom number looks like a northing and easting. Your map is probably on a grid system, the map in one of the corners should say what the system is based off of. Cal have several zones for their state plane coordinate system, or the map could be using just an assumed coordinate system but should have a point to relate to lat/long and/or real world coordinates. Use a geodetic calculator(use google) to convert to std lat/long in degrees minutes seconds.

Tried UTM or Nothing/Easting converters with zone 10, which California is I believe. But the log / lat coordinate came out way wrong.

 

And the map  does not have anything regarding reference point or system using. BTW these maps are date 1969.

 

I'll have to try to get in touch with the agency.

Tried UTM or Nothing/Easting converters with zone 10, which California is I believe. But the log / lat coordinate came out way wrong.

 

And the map  does not have anything regarding reference point or system using. BTW these maps are date 1969.

 

I'll have to try to get in touch with the agency.

 

Are they USGS Quad maps?

Called the agency. She didn't know what system it was used. She said the USGS was commissioned to do the survey for them back in 60's.

 

Are they USGS Quad maps?

 

I am not sure, but this map is titled "Lexington Reservoir" and it does not have the contour of the hills, only the lake.

 

Back in the old days, different agencies used different coordinate systems than the now Standard, WGS84.  Some still do.  The coordinate system used for the map should be stated on the map, or should be accessible from the water agency. I suppose Google would the the best way to find out how to convert the old to the new.  Send a PM to Alpster.  He's a land surveyor, and is very conversant with the more archaic coordinate systems.

 

Sent a PM to Alpster.

Called the agency. She didn't know what system it was used. She said the USGS was commissioned to do the survey for them back in 60's.

I am not sure, but this map is titled "Lexington Reservoir" and it does not have the contour of the hills, only the lake.

Sent a PM to Alpster.

NAD29 woulda been used for a 1960's survey. Next datum that came out would be NAD83, current is HARN adjustment. But not in common to have an assumed coord system that may or may not tie into the state plane.

Just mark up your spots of interest on the paper map, then locate the spots using your sonar via old school method; landmarks. Lexington reservoir off 17 is a small lake, it shouldn't be too difficult to find the ares of interest. When you find the spot, way point it on the GPS.

The coordinates could be Loran C in minutes.seconds?

Good luck, some big bass in that lake.

Tom