Home > Volume 5 Issue 2 > A Lat-Long Code

A Lat-Long Code

Geographical Location information is of increasing value. Almost everyone carries a cell phone. A lot of them are equipped with GPS. Map servers provide good maps and driving instructions. However, there is no widely used coding system for locations easy to use by humans as well as machines. So, now you need to spend several minutes to communicate your destination properly when you are calling for an app-based taxi service, or placing an order online for something you wish to buy. Ideally, there should be a machine readable address code in your cell-phone contacts and you ought to transfer it to an app merely by clicking the contact.

Desired Properties of any Location Code

Ideally, any system for use by humans should have the following properties. Knowing the current address and destination, it should be easy to estimate the distance manually. I should also know in which rough direction I should go. The address should be short and should be usable irrespective of the language of the user. I should be able to read it over a phone call. An app on a cell phone should find its own location and that of any desired destination in this code. The coordinate system must be adequately accurate. When I get to the destination, I should be close enough to where I want to go. I should not have to ask for help from strangers.

The system should in principle be accurate enough for driverless cars as well.

We are almost ready to implement a suitable address-coding sytem. What we need now is a design that is easy to learn and to use. User friendliness is the key. Look at bing/maps or Google maps; you can type in something like “Bengaluru Lalbagh” and locate it on the map. Right click on it and you will get its latitude and latitude coordinates. I list three locations with their coordinates to show the format as it displays coordinates all over the world. The numbers are rounded off to four places after the decimal.

Ashoka Pillar, Bengaluru 12.9439, 77.5852
Sydney Opera House -33.8566, 151.2152
Honolulu, Kahanamoku Beach 21.2836, -157.8392

Consider a system that uses 8 bytes for Latitude and 9 bytes for Longitude. What about locating the address given a truncated lat-long code as shown above? Both map systems mentioned above mapped these codes into a physical location. One did it accurately and the other showed some inaccuracy. I am sure that the inaccuracy can be fixed easily.

A cell phone number with a two-digit country code is 12 numerical digits long, for comparison. So, the lat-long code is not very long. The proposed system can use existing GPS hardware and software on smartphones effectively. It is a worldwide coordinate system. So, users can use a single app worldwide without any changes. The code’s novelty is in being easy to implement and to use.

Consider a location P that has latitude and longitude as follows, using a total of 16 numerical digits plus one comma symbol:
Latitude (8 digits) = Sxx.xxxx and
Longitude (9 digits) = Syyy.yyyy
S is the + or – sign. The proposal is to write northern latitudes as
+13, +45, etc. and to write
southern latitudes as -13, -45, etc.

We propose that the LatLong address of a givan point P be written as

Features of This Naming Convention:

  1. A suitable app on a smart phone can find the LatLong code of any given place on a map. It can point out, on a map display, a location referred by given coordinates.
  2. Given two points described by Lat-Long codes, it is easy to perceive the direction of one point from the other. It is also easy to estimate the approximate distance of one from the other manually. An app can compute and display effective travel directions.
  3. The resolution of this system varies at different latitudes, but is better than 15 meters everywhere. The latitude and longitude circles defined by any point’s latitude and longitude are at most about 40,000 KM in length. If a location is represented on one of these circles using the notation described, the resolution offered in the east-west and north-south directions would each be approximately 10 meters.
  4. It is common in many countries to limit the resolution offered by navigational aids to civilians. The coding system described here needs only map data in the public domain. So, it conforms to usual security discipline.
  5. The student project I suggest is to create an app. It will help locate places on a map, get and use one’s own cell phone location. It will also give driving directions. Google allows developers to write apps interfacing with their code and adding value. We could do that to simplify app building.
  6. It is worth noting that in latitudes like those in India, 1 degree of latitude or longitude is about 110 km. When the latitude and longitude are known in the format described above, maps can show it with an error less than 15 meters.

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