Eugenijus K. needs help calibrating a map of Lithuania, and overlaying a grid in Lietuvos Koordinaciu Sistema (LKS94), the Lithuanian national coordinate system. Here's how to do it using ExpertGPS:

Looking at this map of Lithuania, I can tell that it uses an equirectangular (lat/lon) projection, rather than the Lithuanian Transverse Mercator grid (LKS94). This is because the top left and bottom left corners have the same longitude (20 degrees East), and the top right and bottom right corners are the same as well (27 degrees, 30 minutes East longitude).

To get started, I created a waypoint and recented the Quick Map view in ExpertGPS on Vilnius, Lithuania. I always like to start calibrating a map with some data from the location the map covers. I did a search on Bing.com and quickly found the latitude and longitude of Vilnius, and created a waypoint with those coordinates.

To add the map to ExpertGPS, I clicked Open Scanned Map Library on the Map menu, and then clicked Add. I selected the .jpg file with the map image, and then entered the name of the map, and the projection it uses (Equirectangular).

Calibrating the map

I used three calibration points to calibrate this map. I always try to place the first point in the upper left corner, in this case, at 57 degrees North, 20 degrees West. I placed the second calibration point in the opposite corner, at 53N, 27 deg, 30 min W. Two points are usually enough to properly calibrate a map, and as soon as I added the second point, my waypoint for Vilnius appeared at the correct location on the map. If a third calibration point is required, I try to pick one of the remaining corners, in this case, the lower left one.

Adding the Grid Overlay

To add the Lithunia LKS 1994 grid, I followed these instructions for adding a new coordinate format to ExpertGPS, and selected the LKS grid as shown below.

As soon as I switched to this coordinate format, the grid lines in ExpertGPS switched from showing latitude and longitude to showing eastings and northings in Lithuania's national grid. As you can see in the image below, the grid is centered on 24 degrees East longitude, which runs directly through the center of the country. Because the underlying map is still using an equirectangular projection, the grid lines to the left of the central meridian (24E) curve one direction, and the lines on the right curve in the opposite direction.

Learn More about Scanned Maps in ExpertGPS

To learn more about using your scanned or digital maps with ExpertGPS, read the Scanned Maps tutorials on this site, or Ask the GPS Expert if you need help getting your maps properly aligned in ExpertGPS.

Ryan S. asks:
How do I change an gps address to a longitude and latitude? my address is 25.00.75 80.22.42

Your GPS numbers are in Degrees, Minutes, and Seconds of latitude and longitude (DMS format). The screenshot to the right shows how you'd enter these coordinates in ExpertGPS. Notice that the coordinate format is set to DMS, and the datum is WGS84. If you don't see this format in the Edit Waypoint dialog in ExpertGPS (or in any other coordinate entry dialog), click the Add button.

Converting DMS coordinates to degrees of latitude and longitude

After you've entered your DMS coordinates as waypoints in ExpertGPS, you can convert them all to degrees of latitude and longitude by returning to the Add Coordinate Formats dialog. On the Edit menu, click Preferences, and then click on the My Coordinate Formats tab. If Decimal Degrees (DD) isn't listed, click Add Format, and add it, as described above.

Once you've got both coordinate formats (DMS and DD) added to ExpertGPS, you can switch back and forth between them. Here's the same waypoint you entered using the DMS coordinates above, converted to decimal degrees:

Sending coordinates to your GPS

Of course, if all you are doing is transferring GPS waypoints to your GPS, you don't actually have to change the format in ExpertGPS to match that on your GPS. ExpertGPS does the conversion automatically when sending waypoints to your GPS, so no matter how you enter the coordinates (DMS, decimal degrees, UTM), ExpertGPS will always send the data to your GPS so that it displays at the correct location.

More Coordinate Conversions with ExpertGPS

To learn more about converting coordinates with ExpertGPS, read the GPS Coordinate Conversion tutorials on this site, or Ask the GPS Expert if you need help converting your data.

Sometimes you're given a set of X,Y or Easting,Northing data in an unknown coordinate format. Here are some tricks to make it easier to determine the correct coordinate format using ExpertGPS.

It's usually a simple task to tell the various lat/lon formats apart, but when given unknown gridded X,Y data, it can be difficult to tell if it is in UTM, US State Plane, or a national grid format, since all three use Eastings and Northings. I help ExpertGPS users convert data every day, and I often get emailed X,Y data without knowing the proper coordinate format. If this ever happens to you, try the following:

Where is this data from?

My first question, when an ExpertGPS doesn't know the exact origin of the data, and therefore the coordinate format used, is "what town does this data cover?" For this tutorial, let's try to figure out the correct format for these coordinates: 145537, 4291885, which should be located somewhere around Alpine, TX.

Since the data is in the United States, and these clearly aren't latitude/longitude coordinates, and US National Grid coordinates would be formatted differently, we know we're dealing with UTM or US State Plane coordinates.

Picking the right US State Plane Coordinate System

ExpertGPS.com has a reference list of every US State Plane coordinate system. Clicking on the link for Texas SPCS lists several possibilities: TX South, TX South Central, TX Central, TX North Central, Texas North, as well as the Texas Statewide Mapping System and Texas Centric Mapping System Lambert.

You could try converting your data using each of these State Plane systems, and see which one gives the correct results. Luckily, ExpertGPS.com also lists the counties each of these coordinate systems cover. A quick Google search for "Alpine TX county" reveals that Alpine is in Brewster County. The Texas SPCS page on ExpertGPS.com shows Brewster County is covered by Texas South Central SPCS (as well as the Statewide and Lambert systems).

Comparing your X,Y coordinates to the formats in ExpertGPS

To make it really easy to find the correct coordinate format, I've built a special feature into the Add Coordinate Formats dialog that instantly shows the coordinates for the location you're viewing on the map in each format listed in the Add Coordinate Formats dialog. To take advantage of this, you'll need to load some data for the general area where your mystery data is located. I used the Go to Address command, and had ExpertGPS create a waypoint at the city center of Alpine, TX. With the map centered on Alpine, I clicked Preferences on the Edit menu, and clicked on the My Coordinate Formats tab. I clicked Add, and the Add Coordinate Format dialog appeared.

As you scroll through the list of coordinate formats listed for Texas, you'll see the results of Alpine's location (lat/lon N30.36061, W103.67280) projected into eastings and northings in each Texas State Plane coordinate format. Scroll through the list until you find a sample that is close to the X,Y data you're importing. In this case, TX South Central (Meters), NAD83 gives these coordinates for Alpine: 151671N, 4288824E, which is very similar to (and only a few kilometers away from) our unknown coordinates: 145537N, 4291885E).

Once you've found the correct coordinate format and datum to use, click OK to add this format to ExpertGPS.

Brian H. asks:
How do I add Lowrance gps way point numbers( like 34.06.182 / 81.23.465 and convert to get into google earth pro for fishing way points?

Your data is in latitude and longitude, degrees and decimal minutes. That first dot (after 34 in 34.06.182) should actually be a degrees symbol, or a space. So the latitude is 34 degrees, and 6.182 minutes North latitude. The longitude is 81 degrees, 23.465 minutes West longitude. (In the US, we're in Western Hemisphere, and you'll often see the longitude written with a negative sign: -81 23.465')

Read my tutorial on adding a new coordinate format to ExpertGPS for instructions on how to add lat/lon deg min.min coordinates. You'll need to know whether your data is in WGS84 datum, or NAD27.

Viewing your Fishing Waypoints in Google Earth

Once you've entered your waypoints, you can press F7, the View in Google Earth command, to map your GPS fishing waypoints on Google Earth's color aerial photos. And when you press Send to GPS in ExpertGPS, your waypoints will be transferred directly to your Lowrance chartplotter or GPS receiver.

An ExpertGPS user asks:
How do I enter coordinates in a different format in ExpertGPS? I need to enter coordinates in lat/long and convert to UTM coordinates.

ExpertGPS allows you to work with any coordinate format (lat/lon, UTM, state plane, etc) and datum (WGS84, NAD27, NAD83...) You manage all of these in the My Coordinate Formats dialog.

To add a coordinate format in ExpertGPS, click Preferences on the Edit menu, and click on the My Coordinate Formats tab. Click Add. The Add Coordinate Format dialog will appear. On the left is an expandable list of all of the continents, countries, and US states. As you expand the location tree, ExpertGPS will show the coordinate formats used in that region on the right side of the dialog. Drill-down in the location side as far as you need to go to see the coordinate format for your location. Select the coordinate format, and then choose the appropriate datum from the list below.

Need help choosing the correct format or datum?

Read Solutions to Common Coordinate Conversion Problems, a guide to identifying the proper coordinate format and datum to select for GPS, GIS, and map data in your geographic region.

Converting between two coordinate formats or datums

Here's the process:
1. Add or select your starting coordinate format.
2. Add your data.
3. Select your output format.
4. ExpertGPS instantly converts your data to the output format.

Need more help? There are detailed instructions on Converting between Any Two GPS Coordinate Formats or Datums.

Nick H. asks:
Hi, can i use this program for NZ coordinates?

Yes, ExpertGPS will allow you to work with just about any coordinate format and datum, including New Zealand's North Island and South Island projections (Geodetic Datum 1949), as well as the local "circuit" grids of 1949 and the newer ones using NZGD 2000 datum. (Bay of Plenty Circuit, Chatham Island Circuit, Marlborough Circuit, etc)

Let's assume you want to use the North Island grid, 1949 datum. On the Edit menu, click Preferences, and click the My Coordinate Formats tab. Click the Add button to add a new coordinate format. Change the Location to World/Oceania/New Zealand. In the Format list on the right, click New Zealand North [or South] Island. In the Datum list on the lower right, click Geodetic Datum 1949.

You can add multiple coordinate formats, and switch between them in the My Coordinate Formats dialog, in the Edit Waypoint dialog, or in any other place in the program where you enter or edit coordinates.

To convert between two different coordinate formats, enter your data using the first format, and then make the second format the active one. ExpertGPS will convert all of your data to the second format. You can then export it in that format, print it, or send it to your GPS. (There's no need to convert formats before sending to your GPS, though - ExpertGPS always sends data to your GPS in the correct format so that it is always displayed properly)

Monica writes:
I was wondering about a state correction for NAD 83 in New Mexico. I am not from here, but have an airphoto that I am working with in this specific system. My GPS unit does not have this grid installed. Would you suggest that I purchase a different GPS unit, or should I have this particular map converted? Are all maps likely going to be in this "State specific" grid system?

You're not going to find a consumer-grade GPS receiver that supports New Mexico state plane coordinates, or any of the other US state plane coordinate systems. Garmin and Magellan simply don't include these professional coordinate systems on their consumer-grade GPS receivers.

The easiest way to convert NM SPCS to something your GPS can use (lat/lon, or UTM) is to use mapping software like ExpertGPS Pro. ExpertGPS will allow you to work with New Mexico state plane coordinates and calibrate your airphoto using state plane coordinates. You can then switch the coordinate format in ExpertGPS to latitude/longitude or UTM, to match your GPS. This makes it very easy to convert between state plane and UTM or latitude/longitude GPS coordinates.

Even when you're viewing a map or aerial orthophoto projected using the New Mexico state plane coordinate system, ExpertGPS Pro will be able to convert your GPS data (waypoints, routes, and tracks) back and forth between NM SPCS NAD83 and whatever format your GPS uses (lat/lon NAD27, UTM WGS84, etc) so that your data always displays in the correct location.

To get started with ExpertGPS, download the 30-day trial and follow these instructions for calibrating and geo-referencing your NM NAD83 airphoto.

Jessica writes:
I am doing a behavioral study on a species of bird that has communal display sites called leks. I have set up a 10 meter grid of stakes across a lek, which I use to get x and y coordinates for marked birds on the lek throughout the morning. I have GPS coordinates for each of the stakes and would like to translate the 'fake' coordinates of my grid into real lat and long coordinates. Can you recommend the best way to do that?

Since you're using a sampling grid with 10 meter intervals, the first thing you should do is adopt a mapping coordinate system that uses meters as well - UTM. Latitude and longitude are great for plotting spherical data, but for any type of X,Y data, you should switch to a metric grid system. You could use California State Plane coordinates, but UTM is probably an easier choice, and you can set your GPS to display UTM coordinates.

The next step is to create a 2D coordinate transform, between your sampling grid coordinates, and the UTM coordinate system. This is actually a lot easier than it sounds - you're just solving two equations that map X,Y data from your sampling grid to Easting and Northing coordinates in UTM. You'll need to know the UTM coordinates of the four corner points in your sampling grid. The first should be the zero point, where x and y are 0 in your sampling grid. The second is at the corner (the upper left corner) where y is at maximum, and x is zero. The third point should be at the opposite corner, where x and y are at their maximum. The fourth is in the lower right corner, where x is at maximum, and y is zero.

Solving the Projection Equations

You have to solve two equations. The equation for Easting is: Easting = Ax + By + C. The equation for Northing is: Northing = Dx + Ey + F. C and F are easy to determine - these are the Easting and Northing values at point 1, where x and y are both equal to zero. Because x is zero, the Ax term is also zero. Same for By. So the equation simplifies to Easting = C at the point [0,0]. And you've used your GPS to determine the UTM coordinates at [0,0] are 537305E, 4394972N. So C and F are solved for.

Now consider the upper left point, where x = 0 and y = 200 meters. Because x is zero, the equations simplify to Easting = By + C. We've already determined C = 537305E. y = 200. And the UTM Easting at this point is 537321E. So the equation becomes 537321E = B*200 + 537305E. Subtract 537305E from both sides, and then divide by 200. B = 0.08

Do the same thing to solve for E at this point. Then consider the opposite point, where y is zero, and x is 100 meters. Use the same technique to solve for A and D.

Converting your x,y grid to UTM in Excel

Once you've solved for A, B, C, D, E, and F, you're ready to convert your x,y data into UTM coordinates. Excel or another spreadsheet program is an easy way to do this. You've got your x,y data in two columns. Create two more columns, Easting and Northing. Create a formula for the values in Easting using the equation Easting = Ax + By + C. Same thing for Northing.

Now you're finally ready to map your data. Excel is applying the two formulae to convert x,y data to UTM, using the six constants (ABCDEF) you calculated. Select your data from Excel, making sure you've got the Easting and Northing values as well as the name or label for each data point. Paste this into the Waypoint List in ExpertGPS. Select UTM, WGS84 as your coordinate format (click Add if this format doesn't appear), and be sure to specify that your coordinates are in two columns (Easting and Northing). Enter the UTM zone (it's 13 in the example above). On the next screen, you'll tell ExpertGPS which columns of Excel data contain the Easting and Northing. Once you've done this, ExpertGPS will map your data, and you should see your sampled data points appear on the map right where they should be.

Need Help?

That's probably more math than you want to think about, but the good news is you only have to do it once, and then let the computer do the rest. Those two equations are at the heart of all the mapping features in ExpertGPS - every time you zoom in or scale the map or even move the mouse, ExpertGPS is converting back and forth between the arbitrary x,y coordinate system of your computer monitor and the UTM geographic coordinate system. If you run into trouble, I'm happy to help. Send me the data you're using in spreadsheet format, as well as the coordinates of the four corners of your sample grid, as well as its dimensions.

Setting up a sampling grid using the Grid Builder in ExpertGPS Pro

See that red rectangular grid in the example above? That's the Grid Builder tool in ExpertGPS, superimposing a 10-meter sampling grid over the map. The next time you're setting up a sampling grid using GPS and a map, this tool might save you some time.

Al S. asks:
Will ExpertGPS support USNG coordinates and will it show 1Km grids overlayed onto topo maps as a user selection?

ExpertGPS supports US National Grid (USNG) coordinates. Click Preferences on the File menu. Click on the My Coordinate Formats tab, and click Add. Change the Location to United States, and select US National Grid, NAD83 datum.

You can enter USNG coordinates in the Edit Waypoint dialog, or import them from a CSV file. As you move the cursor over the map, the USNG coordinates for the cursor location are displayed in the lower right corner of the main ExpertGPS window. You can convert lat/lon, UTM, and state plane coordinates to and from USNG by switching between coordinate formats in the My Coordinate Formats dialog.

ExpertGPS displays a kilometer grid when you are viewing USNG, UTM, state plane, or MGRS coordinates. The interval between grid lines is automatically adjusted based on the map scale. At some scales, you'll see a 1KM grid spacing, but as you zoom out the spacing will change to 2KM, 5KM, and 10KM to prevent the map from getting obscured by hundreds of grid lines. You can fine-tune the display of grid lines in the Map Display Options dialog. Or, do what I do, and use the < and > keys to remove or add more grid lines on the fly.

If you want to place a waypoint at every kilometer grid intersection, or create a permanent grid overlay at 1KM intervals, try the new Grid Builder tool in ExpertGPS.

Improving MGRS support in ExpertGPS

Are there ways I can improve the MGRS grid capabilities in ExpertGPS? Post a comment below, or send me an email. I'm always happy to make changes to make ExpertGPS better suit your needs.

Jim D. asks:
Hi, I have and love expertGPS. I've been asked to layout a corner or two for our Placitas Volunteer Library for ground breaking next Sunday. The surveyor of the building sent me, for example, x=1578443.56 y=1567807.68 nad 83, central new mexico, he tells me these are in feet from the principle meridian and baseline. I just want to use my gps, garmin 76 cs to roughly mark a corner or two. Can the expertGPS pro do this, convert to utm's, or lat/long.

ExpertGPS Pro (not ExpertGPS Home) supports all of the US state plane coordinate system formats, and will allow you to enter X,Y data in meters or feet and convert these to lat/lon or send them to your GPS.

To locate the site of your library, I first selected the NM Central NAD83 state plane coordinate system in the My Coordinate Formats tab in ExpertGPS Pro. Do this by clicking Preferences on the Edit menu. Since your surveyor gave you X,Y coordinates that are in US Survey Feet, not Meters, select the second NM Central SPCS entry, the one marked (feet).

Now when you add a new waypoint, you'll be able to enter the coordinates as Eastings and Northings (X,Y) rather than Latitudes and Longitudes. The drop-down list marked Format: lists all of the coordinate format's you've chosen to work with, and so you can now switch back and forth between UTM, lat/lon, and NM Central NAD83 with just a single click. Any time you change the active coordinate format, ExpertGPS Pro will instantly reproject all of your data to the new coordinate format.

To view your newly-marked waypoint in the field, just click Send to GPS. Even though your Garmin GPS can't display NM state plane coordinates directly, you'll still be taken to the right spot. ExpertGPS always communicates with your GPS using WGS84 latitude and longitude, regardless of the display formats and datums you've selected in ExpertGPS or on your GPS receiver.

Related Topics How to Convert Coordinates between Latitude/Longitude and the State Plane Coordinate System Details on all State Plane Coordinate Systems in ExpertGPS Pro