HOW TO FIND A TETRAD REFERENCE

Are you having problems finding which tetrad you saw your birds in? Here are some suggestions.

1. OS map links from this website

If you look at any of the species maps on this website you can hover the cursor over any tetrad to show its name. Clicking will bring up a 1:25,000 OS map (as shown above). Note that the thin blue strip at the bottom of the OS window, covered by the copyright notice and scale bar, is still in the tetrad! e.g. click here for an example map. The Multimap website also now has 1:25,000 maps (see middle column).

2. Grab a Grid Reference utility

This excellent utility allows you to click on a map or satellite image and find out which tetrad you are in. Open the Grab a Grid Reference web page.

3. Aerial photos and maps

Alternatively you may prefer to use online aerial photos. There are two rival systems and coverage is different, so it is worth looking at both to see which is best in your area. These can be incredibly detailed and can pin-point a particular bush, tree or lamppost to one side of the grid line or the other. I have compared the provided grid lines (the yellow lines on the photos below) with detailed OS maps and they are accurate to a metre or so!

a. Link to Google Maps

GoogleMaps maps - good for aerial photos in and around Edinburgh. This link includes the tetrad grid lines. Unfortunately there are no labels (the limit is 200 and we have 1600 tetrads), but see Google Earth, below.

b. Link to Live Maps / Virtual Earth

Live Maps - good for aerial photos across most of Lothian and Borders, but there are still some gaps. This link includes the same tetrad grid lines as used in GoogleMaps (above). Multimap also uses these same images - and you can toggle OS maps (zoom in and you even get 1:25k maps). Click on the 'expand maps' arrow to fill the screen, and if you use IE, the F11 key will give you more screen area still.

c. Google Map side by side with an OS Map

It is possible to compare a Google Map side by side with an OS Map at the excellent Where's The Path website. Note: due to copyright issues the number of map file fetches is limited. The fallback after this limit is reached is this link

d. Download Google Earth

Another method is to use the desktop version of Google Maps called Google Earth. You have to download this free desktop application (8MB download) and run it on your computer with a broadband internet connection. Click on the link above.

To add tetrads and other grids to Google Earth you should also download the following ‘kml’ files (if you download a file, then double-click on it, it will run Google Earth with these data included). NB This file does include labels, but remember Google Earth coverage is only good in some areas. Here are the links to two kml files: Lothian & Borders tetrads (in IE, right click and "Save Target As..."), and GB & Ireland Grid-Lines Layer - a Google overlay of 1-km grid squares

4. Download a tetrad map file for your Garmin GPS

This is not as straightforward as it could be, so only attempt it if you are relaxed with downloading and using free programs from the internet. The process works for a Garmin eTrex Venture which connects via an interface cable to a computer with Mapsource installed. I can't comment on other brands or models.

First, save this image file to your computer (in IE right click on the link and "Save Taget As..."). You will also need two bits of free software: cGPSmapper and MapSetToolKit. You don't actually run the first program, but the second programme needs it to be on your computer. So, run MapSetToolKit and use the following help.

For further help on adding an "img" file to Garmin mapsource software and hence to your Garmin GPS read this web page.

5. Use BTO atlas tools

Link to BTO atlas tools