Drawing overlays in Google Earth


If you contact a landowner or land manager about getting permission it's really helpful to get a map of the area. This can be used by the reviewers when checking cache locations as well as other cachers who may want to place a cache there. The map may be just a hand drawn paper copy (or an image file) or may be a professionally created map using digital mapping software like ESRI ArcGIS.  You may just know the area yourself and can draw it by hand. Whichever way the map is provided it has to be in KML file format so it can be opened in Google Earth by anyone who needs to see it. There are several ways this can be done and each method is explained below.

Hand drawn map of a single area created with Google Earth

Creating a hand drawn map can be done using Google Earth. In this example the landowner of an area of parkland with a country house and garden has provided a hand drawn map with the estate boundaries. The landowner has asked that no caches are placed in the park even though it has free public access. This map has to be transferred by hand to Google Earth and saved as a KML file.

Original map provided by the land owner and email with details of the area and that no caching is allowed (click to enlarge the map).

Dear Chris
I'm the estate manager of Lodge Park in Gloucestershire and I contacted Geocaching HQ after I found a cache within the park and they asked me to contact you and to provide you with a map of the estate so you could stop any future caches being placed there. I'm attaching a file with the estate boundaries drawn. I hope this is suitable.


Fred Smith
Lodge Park Estate

The boundary of this map is now drawn on Google Earth. This is explained in detail below. Click the images to enlarge them. You can also watch a video of the whole process - click here (opens YouTube).
Click the images below to enlarge them

  1. Zoom in on Google Earth to the area you are going to create the overlay in. You can zoom and pan whilst drawing the overlay.

  2. Click the Add Polygon icon on the toolbar (or Add - Polygon from the menu bar)

  3. When the polygon dialogue box opens give it a name and add the description. This is what will appear in Google earth when you click the overlay.

  4. In the Style, Color tab you need to change the default from white to another color otherwise you won't be able to see where you are drawing very easily. Red is suggested at a 40% opacity.

  5. OK the dialogue box so the information is saved. Then right click the new polygon and click Properties. The dialogue box opens again. Now drag the dialogue box to the left and off the main Google Earth screen. It needs to be open while you draw the overlay but not in the way.

  6. Using the mouse wheel to zoom and the left/right/up/down cursor keys to move the map find a place to start. In this example it is the top left corner of the estate. The mouse cursor changes to a cross-hair. Click the mouse cursor/crosshair at a start point. Move the mouse along the boundary to the next point and click again to draw the line. Keep moving the mouse to suitable points and click each time. You don’t need a ‘point’ every few millimetres! As you go ‘round a corner’ it starts to fill in the polygon. The Delete key will remove the last point. If you press the delete key again it deletes the previous point and so on. The last point drawn is blue which means it is the active point. Continue drawing from that point.

  7. If you make a mistake and click a point in the wrong place or miss out a section you can easily correct it but be careful. When you click a new point it connects it to the last ACTIVE point which shows in blue. In this example, (left image) point 1 is the last one drawn - shows in blue which means it's active. Point 2 is in the wrong place. It can easily be corrected by clicking with the mouse and dragging it to the correct location as shown in the second image. But note that now point 2 is blue and active not point 1.

    When you continue drawing by adding the next point at 3 (left image) it actually draws the line from point 2 which is active, not point 1 which you want it to do. Easy to correct, just click delete to remove point 3 and then click on point 1 to make it active and continue drawing.

  8. When you've finished drag the dialogue box back onto the screen and click OK. The area is now saved.
  9. To create the KML file simply right click your mouse on the newly created shape and select Save Place As and give it a name and in the save dialogue box select KML as the file type.

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Hand drawn map of multiple areas created with Google Earth

If the area has several separated parts you can create each one separately in Google Earth but save them as a single KML file for the landowner database. The process to create each area is the same as described in the previous section. First you need to create a folder to store each overlay in. You then save the folder as a KML file.

  1. Click Add - Folder on the menu bar. Give the folder a name and description. Click OK to save the folder.

  2. Now right click the folder and add a polygon. Enter the name and description. You can give each overlay you create a different name and description if required. This information will be used for each overlay when it's uploaded. Change the color and style as shown in the previous section then drag the dialogue box to one side and draw the overlay. Click OK when finished.

  3. Repeat step 2 adding another polygon to the folder and draw the overlay. Keep doing this for as many overlays as you have. In this example there are just two, Millenium Woods north and Millenium Woods south. Finally, right click the folder and Save Place As a kml file.

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Editing a map created in Google Earth - Single overlay

Once you've created a map overlay and saved it in Google Earth you can easily edit it if you need to change the shape. Just open the KML overlay in Google Earth (File - Open) and then right click on it and select Properties. The dialogue box opens and the shape points appear. You can then click and drag the points or add more as required. If you don't want to risk a mistake messing up the original overlay then make a copy of the original KML file and open that to work on.

Be careful when adding new points. The map 'remembers' whether you drew the points clockwise or anti-clockwise and adding a new point may extend the overlay the wrong way. If this happens, just delete the point (delete key) and try the other direction. See the section (7) above on what to do if you make a mistake.

Finally, save the file.

Editing a map created in Google Earth - Multiple overlays

Editing a multiple overlay is the same as for a single one. Open the KML file and you will get the FOLDER with the individual overlay polygons in it. Right click on the polygon you need to edit and make the necessary changes. Then right click on the FOLDER and save that. The edited polygon within the folder will be saved along with all the others.

 Click here for a screen shot showing the folder and polygons of the example used earlier


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Converting digital maps to KML

If you are working with a land manager you may be able to get professionally created digital maps of an area. Ask for these in KML format so they can be uploaded directly to the landowner database but if this isn't possible then ESRI Shapefile format. Some organisations also make their maps available to download. To convert ESRI Shapefiles to KML you can use an online conversion site.

Online conversion. This site http://www.mapsdata.co.uk/online-file-converter/ allows you to upload a file and convert it directly to KML. It is limited to 50,000 rows, and the KML converter approximately 32Mb. If the resulting KML is any bigger it simply won't convert. The conversion process should work OK but sometimes you may find things like the area names and/or description are missing. It depends how the original Shapefile was created. You can edit the kml file to change names and descriptions but you need to know what you are doing.

This example is a digital map of the National Parks in the UK which can be downloaded from a government website called Natural England. The file is downloaded as a zipfile in ESRI Shapefile format. The zip consists of several files which contain the map data, coordinate format and so on. Simply 'drag n drop' the zip file on the conversion site and a few moments (minutes if it's a big file) you get the prompt to download and save the KML.
Click to enlarge images

There was a problem though with this particular file. The file has names for each of the parks (Peak District, Yorkshire Dales etc) but there is no description. This means when viewed in Google Earth you don't know why what the area is for. Editing is relatively easy using Notepad++ (free to download) or any good text/script editor but you will need to know about editing such files and their structure. You could also open the file in Google Earth and add a description there.