Converting latitude and longitude to Israel Transverse Mercator (ITM) coordinates

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The standard coordinate grid in Israel is called Israel Transverse Mercator (ITM), and is sometimes informally referred to as the "new Israel grid" (רשת ישראל חדשה). This grid appears in detailed maps of Israel. Nonetheless, the older and less accurate Israel Cassini Soldner (ICS) grid or "old Israel grid" (רשת ישראל ישנה) is also still used in many places. For example, despite the official adoption of ITM in 1994, the ICS grid is still displayed more prominently in Israeli hiking maps (מפות סימון שבילים) and is consequently more commonly used by hikers.

The ITM grid is a transverse Mercator projection, meaning that the surface of the earth is projected onto a cylinder whose axis of symmetry is parallel to the equator. This provides an accurate projection along a longitudinal slice of the earth, with the inaccuracy increasing as one moves away from this axis. Thus, for example, the Universal Transverse Mercator (UTM) grid divides the earth into 60 longitudinal slices, each projected separately. Since Israel is a narrow country, whose span from east to west barely exceeds 100 kilometers, a single projection is sufficient for accurately representing the entire area.

To demonstrate how this grid can be used, I wrote a JavaScript program which can be used to convert a latitude and longitude position to ITM coordinates (below). The accuracy of the ITM projection is quite high and the error does not exceed 10 meters. This program also provides approximate conversion to the old ICS grid. However, since the ICS grid uses a different (and inaccurate) projection, the ICS values may be off by as much as 200 meters.

Latitude: ° North
Longitude: ° East
ITM: -
Old Grid: -

The program was written based on an Excel spreadsheet for computing transverse Mercator projections, written by Steve Dutch of the University of Wisconsin–Green Bay. Feel free to download and modify the source code for this program (included in this webpage).

I also converted this program to a Java midlet which can be used on Java-enabled smartphones equipped with a GPS. To use the midlet, you will need to download the midlet jar file and, depending on your phone, possibly the jad file as well. You can also take a look at the source code if you are interested. This midlet accesses the smartphone's GPS, retrieves the current position, converts the position to ITM and ICS, and displays the results on screen. The altitude above sea level and the GPS accuracy are also displayed. The same conversion algorithm (actually, the same code) is used, so the same caveats concerning accuracy apply here as well.

Alternative ITM conversion programs

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