GPS use and mapping in humanitarian applications

About OziExplorer

OziExplorer is an application that runs on devices that use an MS Windows operating system.  It provides interaction between a georeferenced map image and a GPS unit facilitating the transfer of tracks and waypoints.  It provides extensive map documentation features.

    Application of the OziExplorer approach – broadly what is required – working environment

The MapToGround site provides support for two humanitarian field navigation and data acquisition methods.  One of these methods, the use of KMZ map image files on handheld devices is covered on the KMZ and GPX files page.  The other method, using OziExplorer, is discussed here.

The OziExplorer system requires a computer device with a Windows operating system, a basic GPS receiver that is interfaced with the computer by a serial, USB or wireless link and a registered copy of OziExplorer software.  The method would probably fit sensibly into a stable-office-team-members-collecting-field-data situation.  The cost of the OziExplorer software would be covered by the lower purchase price of basic GPS receivers as compared with GPS receivers with map display features as required by the KMZ file approach.

The OziExplorer method provides good documentation facilities.  Documentation can readily be transferred electronically as OZiExplorer or PNG image files.

    Process – how it works – MAP files – MapToGround resources

The ingenuity of the method is due to Des Newman of D & L Software Pty Ltd at OziExplorer.  Only a fraction of the features of OziExplorer are presented on this page.  MapToGround's intention is to condense Newman's method to the particular requirements of the humanitarian aid worker.

Briefly described, OziExplorer allows the user to load and calibrate (georeference) an electronic map image so that interfacing with a GPS receiver is meaningful.  The sources of the electronic map images are diverse; computer constructed maps, scanned hard copy maps, aerial photographs or satellite images can be used.  After calibration, data (waypoints and tracks) in the GPS receiver can be transferred over a serial or USB link to the map image and data on the map image can be transferred to the GPS receiver.  Additionally OziExplorer will import and export data as GPX files.

The outcome of the OziExplorer map image calibration process is the creation of a MAP file.  A MAP file relates grid references on the map image to pixel positions.  It is a text file of several kB.  MAP files can be transferred from user to user.  It is not difficult to produce a MAP file, but it is more sensibly done at relative leisure off-field rather than during the pressure of deployment.  MapToGround provides MAP files to accompany the maps produced by UNOSAT, WFP Logistics Cluster, WPF Map Centre ZKI, and MapAction.  MapToGround also provides each appropriate map image as a JPEG file for loading by OziExplorer or alternatively provides a direct link to the appropriate map image file on the agency site.  Occasionally MapToGround produced MAP files include additional cartographical information.

    What is required – detailed
  • Handheld GPS receiver with computer interface ability (map display features not required) – "most Garmin, Magellan, Lowrance, Eagle, Brunton/Silva and MLR GPS receivers".  OziExplorer details

  • Computer with MS Windows operating system – "95/98/ME/NT4/2000/XP/Vista/7/10 (both 32 bit and 64 bit versions) /Windows 7 Starter/8 and 8 Pro (will NOT run in Windows RT)".  OziExplorer Android will run on devices with an Android 2.0/2.1/2.2/2.3/3/4/5+ operating system.  MapToGround has not had experience with OziExplorer software other than the PC version.  OziExplorer details

  • OziExplorer software – OziExplorer is available on disc or by download.  Two trial versions are available and allow an investigation of the software before registration.   MapToGround assumes that the user is running a registered version of OziExplorer.  OziExplorer details

  • Internet access – continuing internet access is not required, access is required initially to download a map image (typically several MB) and the map file (several kB), but not thereafter.

  • A basic understanding of GPS, map grid reference and datum.  navigation basics
    Setting up – installation

If possible, it would be sensible to do these exercises prior to humanitarian deployment.

1) Install OziExplorer, when you are satisfied that it is working in demo mode, register it.  Work through the tutorial (Help – > Tutorial).  Skip the Calibrating a Map section (about two screens deep) – MapToGround has done the map calibration for you.

2) Adjust the configuration settings (File – > Configuration)  In particular –

System tab:    set Data File Datum to WGS 84

Maps Tab:    set as in figure below

GPS tab:    set both datum boxes to WGS 84, set the GPS parameters appropriately (refer to your GPS receiver handbook and OziExplorer help)

COM tab:    determine if your GPS receiver uses USB or serial communication.  If serial, determine baud rate from GPS receiver data sheet.  Serial ports are being discontinued.  If there is a single serial port (DB9 male connector) on your computer it will most likely be COM1.

3) Check the MAP files supplied with OziExplorer (located in .. \OziExplorer\Maps\Example Maps – possibly in C:\Program Files\OziExplorer\Maps\Example Maps) to see if there is a map that covers your present location.  Generate some waypoints and tracks on your GPS receiver and test the uploading procedure.

If there's not a suitable map in the OziExplorer examples for you to experiment with, email MapToGround and provide your general location and the name of the aid organization you are associated with and MapToGround will try to generate a suitable test map image and MAP file.

    Android Devices – file conversion – MAP file generation

Discussion on the use of OziExplorer on Android devices can be found at this OziExplorer reference.  The map image file formats directly or indirectly provided by MapToGround are either JPEG or PNG.  Because Android devices will not load these formats it will necessary to convert such files to the OziExplorer OZF4 format.  The conversion (and uploading to the Android device) of files can be done using the OziExplorer program, Img2ozf, available at the Img2ozf download page.

It will also be necessary to generate a OziExplorer MAP file to match the OZF4 file.  There are two methods available:

  • use the 'Load and Calibrate Map Image' function of OziExplorer in the normal fashion to generate a new MAP file or
  • edit an existing MAP file.

The second method may be applicable when the calibration points on the map image file are not readily apparent.  Contact MapToGround for further details on the second method.

    OziExplorer and JPEG files – jpg and jpeg file extensions

JPEG (Joint Photographic Experts Group) files commonly have jpg or jpeg file extensions.  Map Action JPEG files have jpeg extensions.  Unfortunately the current version of OziExplorer does not recognize the jpeg extension, it is necessary to rename the jpeg extension as a jpg for use with OziExplorer.

Introduction to some further OziExplorer features

The following boxes introduce some OziExplorer features that may be useful in the field.  They represent only a small part of the capabilities of Oziexplorer.  This section attempts to show what is available, not how to do it.  Comprehensive information can be found in OziExplorer help.

    OziExplorer file types – *.map, *.wpt, *.plt, *.ozf4

The following file types are particular to OziExplorer.

MAP:     The principal purpose of a MAP (*.map) file is to provide calibration for the map image by relating geographical location to pixel position (georeferencing).  The MAP file can also contain user provided data (for example, notation) that will be displayed when the file is opened in OziExplorer.  In addition the MAP file can control the interaction of other files with the map image.  In essence it manages the interaction of various components of a mapping project.

WPT:     A WPT (*.wpt) file contains a list of waypoints saved from OziExplorer.  The waypoints may have been entered into OziExplorer by the user or uploaded from a GPS receiver.  Conversely a WPT file can be loaded into a map being displayed in OziExplorer and then uploaded into a GPS device. 

PLT:     A PLT (*.plt) file contains a sequence of points that define a track saved from OziExplorer.  The track may have been entered into OziExplorer by the user or uploaded from a GPS receiver.

OZF4:     A OZF4 (*.ozf4) is a map image file format that has particular advantages when used with OziExplorer.  It is the preferred format (over JP2 and ECW formats) for use on Android devices.  OziExplorer reference.

    Documenting the map with map objects

The 'postcard' files illustrated in this section are available as

The original map image.  The images that follow were created from OziExplorer with the File->Save Map to Image File function.  (The mouse-over features available in OziExplorer do not work on these images.)

A more complex example of the use of map objects is presented in the OziExplorer tutorial available via Help->Tutorial (Demonstration Data).

The text on this image has been placed using the comment object.  The user may specify text colour, background colour (including transparent), font size and normal or bold fold.  The comment data are embedded (on saving) into the map file.

The two red dots on this static image do not give an adequate indication of the usefulness of the feature object.  The feature object has these properties.

  • Symbol – there is a selection of symbols available for display. 
  • Mouse-over – the name and location of feature is presented.
  • Comment – a comment can be attached to the feature.  This comment can be viewed in the properties dialogue box.
  • Attachment – a file of any format can be attached to the feature.  The attached file can be opened from OziExplorer.  Thus with a couple of mouse clicks the user may have access to the bore water quality report or the image of the view from the peak.
  • The feature data are embedded (on saving) into the map file.

In the sample file set,, a right mouse click on the bore feature will enable the user to access the bore report.

Waypoints may be displayed after they have been uploaded from the GPS receiver, loaded from a file or have been entered by by the user.

Data files can be attached to waypoints.  In the sample file set,, a right mouse click on the view waypoint will enable the user to access the view.

Waypoints can be saved as a waypoints (WPT) file.  This file can be attached to the map file and and on future occasions the waypoints will be loaded along with the map image.

To attach waypoint or track files to the calibration file so that they will load automatically choose the Check Calibration of Map option on the File Menu, click the Options button in the calibration frame and the Map Advanced Options dialog will be displayed.  Click the Open Folder button on the edit box (to the immediate left of the Add button)and select and add files one at a time.

There are two tracks displayed on the map – one is cosmetic and simply underlines the map title, the other indicates the access to the bore.  Tracks can have originated from the GPS receiver or they may have been entered by the user (clearly the underline is such a case).  Tracks can be saved in a tracks (PLT) file.  This file can be attached to the map file and on future occasions the tracks will be loaded along with the map image.  The colour and width of the tracks is selectable.

    Distance and area measurement

Single leg and accumulated distances can be displayed.

The area is defined by successive mouse clicks.

    Constructing a map from a blank sheet – starting from nothing

OziExplorer has an effective arrangement for the user to construct her own map.  Data are collected from site to be loaded into a blank template.  OziExplorer generates a map file that sensibly positions the data and defines an appropriate scale.  As further field data are connected they can be loaded onto the map.  Layouts can be designed on the map and then transferred ground using a GPS receiver.

The map (extract to the right, full size available) was constructed with waypoints and tracks from the field.  The access route, the water course and the three dams are field data.  The boundary was added in OziExplorer by linking waypoints obtained in the field at the boundary corners.  The dams were filled by selecting type polygon for each track around a dam and an appropriate fill colour.

The map is at a relatively large scale (less than 1 metre per pixel, approximately 2,400:1 on my monitor, and is approximately 1.3 km by 0.9 km).  As a consequence the tracks appear angular because they are formed from a small number of points.  More careful use of the GPS receiver track record options could have alleviated this effect. 

Click extract to view a complete image.  The files used to build the 'blank' map are available as

Updated: 24 July, 2018       MapToGround introduced July 2010.       site management