Tag Archives: map

Converting Map Coordinates for Bushwalkers | Latitude, Longitude to/from UTM

Ever wanted to understand what the numbers on the lines on your map are? Does your iPhone app only register latitude and longitude and you need to convert it to UTM (Universal Transverse Mercator) or vice versa. Need to be able to tell your local emergency service the latitude and longitude of your location for a rescue?

There are at least three ways to convert between coordinate systems or formats eg UTM grid references to latitude and longitude

  1. using an online Web Converter (see below for examples)
  2. install an iPhone App which does it for you (see below for two)
  3. change your GPS  coordinate format settings and see the converted result

A word of warning from Professor Dutch

“Caution! Unlike latitude and longitude, there is no physical frame of reference for UTM grids. Latitude is determined by the earth’s polar axis. Longitude is determined by the earth’s rotation. If you can see the stars and have a sextant and a good clock set to Greenwich time, you can find your latitude and longitude. But there is no way to determine your UTM coordinates except by calculation.(Source: Steven Dutch, Natural and Applied Sciences, University of Wisconsin – Green Bay)


“Universal Transverse Mercator (UTM) coordinate system is a grid-based method of specifying locations on the surface of Earth. The UTM system divides the surface of Earth between 80° S latitude and 84° N latitude into 60 zones, each 6° of longitude in width and centered over a meridian of longitude. Zones are numbered from 1 to 60. ” (Source: Clever Applications)

Some Online Web Converters

iPhone Apps

Map Tools screenshot

Map Tools By Richard Hoffman

“Map Tools is an iPhone app  that let users to fully utilize coordinates. Map Tools converts coordinates among various datums, coordinate systems and map projections. It also calculates distance between two coordinates. It supports coordinates conversion between geodetic coordinates, UTM, UPS, MGRS and map projections in up to 232 datums. The app is delivered with WGS84 ellipsoid and used as the default datum. You can purchase an add on that will provide you with an additional 232 datums, which include NAD27, ED50, OSGB36, EGSA87, AGD66, AGD84, GDA94 and a lot more.” (Source: iTunes Apps)

NB for Australians WSG84 (supplied) and GDA94 are almost equivalent so if you are only using this datum there is no need to buy the extra 232 datums. 

Bit Map by Nixanz 

Bit Map by Nixanz

Bit Map is a map viewer app with some basic GPS features, and simultaneously provides both the UTM and latitude/longitude coordinates in decimal degrees for any point on the uploaded map you are viewing. While it doesn’t convert between map coordinate systems, it will give both for any location and datum.

Read my Review of Bit Map

Using your GPS to convert

If you open the settings field on your GPS, you can change between the coordinate formats offered eg UTM to Latitude and longitude etc and all coordinates entered in the original format will then appear in the new.

Social Bookmarking

Visit my Delicious bookmarks to discover some popular web resources on this topic.

Further Reading

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This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.


iPhone Navigation and Map Viewer App Review | Bit Map 3 by Nixanz

Do you want to be able to view your hard copy or digital topo bushwalking maps on a high resolution, user-friendly, portable viewer? Want to know where you are on your map, even when outside your mobile’s reception area? Want to carry one less device with you while on your bushwalks?

I always have a second look when I see an iPhone app with a local flavour and Bit Map by Nixanz meets this requirement. The developer, Nik Sands, is also a Mac enthusiast which automatically makes him a friend of mine, keen bushwalker, Bushwalk Australia forum administrator/founder, and has produced some useful applications for the Mac which makes this iPhone app especially worth checking out. His OZF viewer  is a great free application for viewing map files with the OziExplorer (.ozf2) suffix.

Bit Map iPhone App

In the past, I have used software such as MacGPS Pro (see my review of the latest version) to view topographic maps which I have scanned, stitched together and loaded into my mapping software. I have plotted routes and waypoints using MacGPS Pro and then uploaded these to my small GPS (Garmin Geko 201), which has shown the route clearly but lacks the background detail, such as contours and features, shown in a topo map. I have found that being able to zoom a laptop screen image to place a waypoint or find the coordinates is much easier than struggling on the original topo map with a magnifying lens as I once used to do. I have often tracked my route with my GPS and downloaded it on my return to MacGPS Pro to view exactly where I had walked.

Niche Market

The developer Nik Sands designed this iPhone app to meet a need for Australian bushwalkers which was not being met by existing devices and software.

Bit Map fills a niche market for bushwalkers who need to view Australian 1:25K or 50K  topographic maps in colour and wish to have the benefits of a user friendly, portable map viewer which can view the maps offline, without the need for mobile reception or a wifi connection. The iPhone with its large, high resolution colour screen (version 4’s retina display shows 4 times as much map without loss of image quality as the iPhone 3), large storage capacity for maps and user-friendly touch screen, makes all this possible. This app’s primary task is to convert your iPhone into a high resolution map viewer and is not designed to replace your dedicated GPS, although for many people it will be more than adequate. It has many of the basic  GPS’s features you would expect such as giving the grid references of your location, speed and allowing you to enter waypoints and upload routes.


Bit Map Screenshot

Unlike expensive proprietary maps which need to be purchased, such as the vector maps of Garmin, and then uploaded into a matching GPS, Bit Map works with bitmapped or raster images which can be user-supplied and produced in a variety of traditional graphic formats such as JPEG, PNG, TIFF, GIFF and even PDF.  In addition, Bit Map  can import OziExplorer maps (OZF2) which are pre-optimised,and are highly regarded in Australia. Maps need to be supplied by the user as there are none built-in, except for a bundled map of the world.


Once converted into a supported digital format, maps need to be optimised for use in the iPhone and this can be done within the iPhone or on a desktop computer using third party software, which is the preferred option, and Nik has supplied some software for this purpose. Pre-optimisation saves lengthy load times as the iPhone doesn’t need to do as much processing.

“When you first download a map to your iPhone, Bit Map will automatically split it into small chunks that are easier for the iPhone to handle and will compress each chunk to reduce the amount of storage space used. While viewing the map, each chunk will be seamlessly loaded when it comes into view on screen.” (From developers website)

Optimisation stores the maps as JPEGs at 50% quality to save storage space, which will of course result in a small loss of quality.

Maps can be downloaded directly using the built-in web browser if you have wifi access or a large data plan.

In Map View, the UTM zone and grid reference of the current location overlay the map along with the latitude and longitude for the WGS84 datum, and the estimated recent and average speeds.  The grid reference defaults to the WGS84 datum if there is no current map datum available.


“There are two methods of calibrating map files:

The fully manual preparation method requires you to determine and define the region of the Earth covered by each map yourself, and to rename each image file using a strict format to define each map’s area.

The .map method uses OziExplorer-compatible “.map” files to automatically determine the area covered by each map, but is only available to OziExplorer users, or people who’ve obtained maps with associated “.map” files in OziExplorer format.If the image is not pre-calibrated (eg ECW, GeoTIFF) then it will need to be done manually by clicking a few known points and adding their coordinates.” (From developers website)

Installation of Map Files and KML, KMZ files

“Maps (converted and calibrated as detailed above) and KML files can both be loaded into Bit Map on an iOS device (iPhone or iPad) using much the same process.  There are three different ways for Bit Map to load maps and KML files.  Choose whichever of these methods suits your circumstances the best:

   1. Using iTunes’ file sharing over USB.  This is by far the fastest (by several orders of magnitude) and easiest method if you are able to physically connect the device to a computer running iTunes which also has your map or KML/KMZ files on it.
   2. Uploading files via WiFi from your desktop/laptop to Bit Map, directing the web browser on your Desktop/Laptop to the URL that Bit Map displays in its acquisition view.  While in the acquisition view, Bit Map will run its own built-in web server ready to receive files from web browsers on the local network (NB:  The desktop/laptop uploading the files must be on the same local network as the iPhone running Bit Map, and Bit Map must be displaying it’s acquisition view for this to work).
   3. Downloading files from a web server somewhere on the internet (or on your local network) using URLs that you enter into Bit Map itself. This means that you first need to upload your prepared map image files to a web server. Any computer can act as a web server, so long as it is configured correctly. If you don’t already have upload access to a web server, you may be able to set up your desktop/laptop as a temporary web server.”(From developers website)

GPS Functions

Bit Map screen shot

“Bit Map can record and store several routes (series of waypoints).  Waypoints can be named, and several routes can be displayed on the map simultaneously.  Routes can also be sent to or received from your desktop computer as KML files which can be read by a variety of other applications, including Google Earth.” (From developers website)

Unlike MacGPS Pro it can’t show profiles, nor load some of the more unusual formats available. It overcomes some of these limitations by allowing the import of .kml and .kmz data already prepared on a desktop computer using software such as MacGPS Pro and the export of any such files generated by email.

Bit Map uses the iPhone’s built-in GPS to show your current location on your map and also has the ability to “follow” your location if you are mobile, by centralising the map on the screen as you move, loading new maps as required.

“While in ‘Follow’ mode, sleep is disabled (only while connected to a power source) and the map is continually scrolled to centre on your current location”. (From developers website)

As with many iPhone apps that use the GPS, there is a potential for your battery to drain quickly. (See my recent post “How to Keep your iPhone Charged in the Outdoors“)

Browse the developers website for more Bit Map information.

Bit Map Settings Screenshot


The iphone with Bit Map installed will never match my 17″ MacBook Pro with MacGPS Pro installed for ease of viewing, profiling and entry of waypoints and routes, nor will it match a dedicated GPS for battery life or robustness, although there are solutions to both these problems. Hopefully you will not need to use your iPhone in heavy rain or when wearing gloves.

It does however provide a compact and mobile map viewer with a limited set of GPS features which will suit many people who don’t need the full range of GPS features and in the past have relied upon large laminated paper maps. For some it will mean their GPS will no longer need to be carried on a bushwalk as their phone will do both tasks.

Congratulations Nik on a job well done!

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This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Why use navigation software with your GPS?

MacGPS Pro screen capture

Navigation software has many advantages over using a map, compass and measuring device to plan a route. Two of the best are the time savings and the increased accuracy.

For many people a key advantage will be the ability to zoom in and enlarge what you see, making it easier to count contours and recognise symbols. For others it will be the ability to position the cursor on the map at a point of interest and read the grid reference with high accuracy, without any need to physically measure.

For most, it will be to plan a route, by clicking a series of carefully selected waypoints, naming them and then exporting the waypoints to a  kml file, which can be viewed in Google Earth. If like me, you have a lightweight small screen GPS eg Garmin Geko 201,  then the time saving is enormous, compared to having to enter each waypoint manually using the rocker button, to repetitiously scroll through the alphabet.

Garmin Geko 201

Want to get a bearing between two points? Simply click your cursor at the first point and drag to the second and read the result.

Want to measure the distance along a route? Simply click a series of points along the route, the closer together the more accurate,  and then read the result.

Want to see how your actual route compared with that planned? Simply import your GPS data back into your computer and look at the points on your map.

Your mapping software is your interface between your map and your GPS and as such, the quality of your map is critical, but that’s another story for later.


For Mac users:

Navigation software: MacGPS Pro
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This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Can my GPS replace my map?

Ever thought that with the purchase of your upmarket colour screen GPS that you don’t need to take a map with you any longer? Wrong, wrong, wrong …..

Many years experience with using GPS on bushwalks has convinced me otherwise.

Ever had your batteries go flat at a critical time? Ever had your GPS freeze and then reset itself to factory settings wiping all your waypoints and routes when you have rebooted it? Ever dropped your “waterproof” GPS onto rocks and had it bounce into a nearby waterhole and then slowly sink as it fills with water? Ever struggled with the buttons on your GPS  in the dark while wearing gloves?

Well I have and that’s why I always take a map as my primary navigation tool.

I use my GPS to check my location at each stop, to find a difficult campsite or waterhole, or the precise turn off from a ridge line down a spur. I haven’t yet, but I might one day use TRACKBACK to return to a previous known point when I am geographically embarrassed. I sometimes use it to estimate walking speed so I can estimate how long it will take to reach a campsite. With some GPS you can determine sunset, sunrise and tides, which can be very useful information on some bushwalks. I have used it to find altitude and therefore help me determine my location on a known track or to work out how much further it is up to a saddle. Of course some of these can be done with a map alone, but often it involves calculations and looking for labelled contour lines.

Normally I don’t have my GPS turned on continuously during a walk but there are times when its fun to get back home and be able to trace a difficult or off-track route on a map or Google Earth or to determine your walk profile using elevations. If you take lots of photos, there is software that will link you photos with the GPS location using your time log, assuming you have the clock on your camera set correctly to the same time -zone.

I use my map to give me the big picture, orientate myself, show local topography and allow me to follow my route continuously by reading “map-to-ground” and by “thumbing” the map. It takes lots of practice but is very rewarding. I actually enjoy map reading, anticipating what I will see around the bend and looking at my surroundings as I walk. As my map reading skills improve, I find myself using a GPS less and less.

The danger with a GPS is that you are so engrossed looking at the screen that you don’t actually see your surroundings. If you become “lost” then you have no mental image of the route you have taken to get you back to a known point.

Murphy’s Law can be guaranteed to ensure that at the point when you need it most that your GPS will fail!

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This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.

Why am I lost when I have a GPS?

Ever wondered how you could possibly get lost while carrying a GPS, and when you do get geographically embarrassed, whether you can trust your GPS?  

I’ve sometimes been acutely embarrassed when my high-tech equipment has been worse than useless on a difficult walk where spot-on navigation was essential. More than once,  I’ve found myself on the opposite side of a creek or on the wrong ridge-line. Sometimes I’ve returned from a walk to find that my route lay parallel to that shown on the map, but about 200m away. How could my GPS get it so wrong?

Well of course my GPS hasn’t got it wrong, it has been simply calculating position based on the incorrect settings I gave it. The indication that you’ve incorrectly set your GPS is when every feature is in the wrong place by a consistent amount.

If the error is about 200m then you have probably set your GPS to the wrong map datum eg you may have chosen Aus Geod ’84 or Aus Geod ’66 when your map shows the correct datum to be GDA94 . Your GPS must be set to the same map datum as  the map you are using.

For my Garmin Geko 201, the following datums are relevant when using Australian maps.
    Aus Geod  ’84 = AGD84
    Aus Geod ’66 = AGD66
    GDA  =GDA94
For Australian maps, the common map datums you will find are
    AGD66 (oldest)
    GDA94 (most recent)

Fortunately, all you have to do is to make sure that the map datum to which you set your GPS matches the one shown in the legend on your map. To do this for a Garmin Geko, select SETUP from the menu, then UNITS from the sub-menu, then MAP DATUM, and scroll down the list to select the correct one which matches your map.


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This article by Bush Walker is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.