GPS is one of the most fantastic utilities ever devised by man. GPS will figure in history alongside the development of the sea-going chronometer. This device enabled seafarers to plot their course to an accuracy that greatly encouraged maritime activity, and led to the migration explosion of the nineteenth century. GPS will effect mankind in the same way. There are myriad applications, that will benefit us individually and collectively.
Latitude, Longitude, AMG etc etc etc:
I get many requests to explain the different numbers used by different GPS at the same location. This is a valid and sensible question, and there are easily understood answers. You may also wonder about terms such as UTM, GDA, MGA, datum, position format, grid, and true north. My customers get free assistance with these, and any other matter relating to their purchase, and the use of the GPS.
- What is GPS? (Explaining the system of satellites and how it works)
- Correction techniques for greater accuracy (DGPS)
- Elevation readings and GPS (How far are we above sea level?)
- The theory of positioning (How Sir Isaac Newton and others made GPS possible)
- Explanation of digital mapping forms and functions in relation to GPS
- Applications for GPS
by Kimball Thurlow, 2002, ©, Johnny Appleseed GPS, Brisbane
Forms of Digital mapping
- 1. Raster maps: Digital mapping is available to cover all of Australia at various scales. This mapping is usually scanned from paper maps or aerial photos, and is called raster mapping. (Raster, because it is made up of collections of pixels, or is a bitmap).
Raster mapping has the advantage of reproducing exactly what we see on paper, including shading, colouring, features and contour lines. Raster maps are one scale only, you cannot decrease the scale without losing resolution, because the image becomes "pixelated".
- Vector maps: The other type of digital mapping is called vector mapping. This is because it is made up of simple instructions like a program. For example:
- 1. Join points 2 and 3 with a red line 2mm thick.
- 2. Join points 2 and 4 with a black line 0.5mm thick.
- 3. so on.
Vector mapping has the advantage of being able to be searched for names, words and phrases. In effect, it is its own database, so is much more useful in a "find where" situation. It is also scaleable, that is it remains in focus regardless of scale.
Using maps in GPS
Raster mapping:
This type of digital mapping is used by programs such as Oziexplorer or Memory Map, for use on a computer, tablet or PDA, often in conjunction with a GPS signal. Raster mapping is produced in Australia by
Geoscience,
Maptrax,
Memory-Map and others. From raster maps, you can load points, routes and tracks, either manually or by computer cable, to most GPS.
You can also load raster maps to some Garmin units, and this is
shown here.
Vector mapping:
GPS, whether hand-held, marine, or in-car, is used mainly to guide you to a destination. Vector mapping is more effective in GPS, because it is searchable for names and places. Vector mapping is also used in GIS products.
All the cartography, marine and land, supplied by Garmin, is in vector form for more effective "find" and guide functions. Vector mapping is released by Garmin worldwide under the
Mapsource brand. Other vector mapping is supplied by
Geoscience and Johnny Appleseed GPS.
Maps can be in two forms - digital (on a computer or GPS screen), or on paper, the more traditional mode. Either way, the following information applies.
- Maps are produced to model information on the earth's surface.
- Maps are produced to scale, so that positions on maps have the same relationship in scale, as the real objects.
- GPS can display and log real positions on the earth's surface. These positions can then be interpreted on any map.
- Naturally, the datum or origin on the map must be the same as the GPS.
- Johnny Appleseed GPS can ensure that your GPS is set to agree with whatever maps you are using.
- Johnny Appleseed GPS can also show you how to scale, and load or retrieve points between the map and your GPS.
NATMAP, DNR, HEMA, and WESTPRINT paper maps, compendiums, and Atlases.
For that round Australia trip, or for local national park information!
Modern Australian mapping is in full colour, easy to read symbols, and ready to use with your GPS. Mapping is available for the whole of Australia and territories.
Staff at Johnny Appleseed GPS can show customers how to relate mapping to GPS - out there when it counts.
A simple map reading guide, and map scales make it easy. The only problem still remaining, is how do you fold the d___ thing!
from 1:25,000 9132-I-S copyright CMA NSW
Remember, if you ever happen to be lost or in danger, with or without a map, a PLB will bring assistance fast.