Making a Rogaine Map - NSW Rogaining Association

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• Angle to the grid/magnetic angle. • Grid distance to the grid line spacing. Make the two offsets a whole number of thousands of metres otherwise you will get very unfriendly numbers on your grid scales around the border of the map. Drawing the map Choose "Template/Open" and select one of your scanned blocks. If the scale of your base map is a different to the final scale, set the "Draft scale" to match the final scale. Set the Rotation to the Grid - magnetic angle. Click OK. The template will appear in the middle of the drawing window. Zoom out so you can see both the template and the area where it should be. Choose "Template/Adjust (F9)" and using just one point move the template to approximately the correct position. Now zoom so that the template and the position it should be are just in the drawing window. You can now adjust the template accurately using four points set to the outer grid corners of the template. Zoom in on each corner then zoom out to get best accuracy. OCAD supports nested commands. You will often find you can't achieve an exact fit. This is because grid squares on the base map are not square unless you happen to be in the middle of a zone. The OCAD grid is a perfect square. This is one of the reasons for scanning the map in small sections.. When you come to draw an adjoining section you just have to tweak the contours and other lines that cross your section borders so they join up. If you are working from photogrammetry or other source that did not have a grid, you should first draw onto the map any known features. If there are roads or tracks that show up on the photogrammetry, spend a few days in the field recording their position using your GPS and draw them onto the map using the methods described further on. Now check the position of your template against these features. If any are significantly in error, try readjusting. You may find you have to break the template into smaller areas. You can now start to draw the map. Some points to consider ... • Use bezier curves for all curved lines. Once you get the hang of it it is the fastest method and most definitely produces the best result. • Don't merge long lines such as contours where they cross your block boundaries. If you happen to accidentally delete or move one later on it will be more obvious and easier to fix. OCAD remembers the adjustment of each template so it is easy to reopen the template to check something. When you "Open" and "Adjust" a template, the position of the template is saved as part of the map.ocd file. If you "Close" the template you can then "Reopen" it and it will be in its adjusted position. Doing an "Open" will lose any previous adjustment. OCAD uses absolute addressing to store the location of the template file so if you pass your work to someone else you need to pass the directory structure. To draw magnetic north lines on the map, choose "Options/Scales" and change to "Paper coordinates" and set the "Grid distance" to a value that equals the spacing you want for the north lines. This would typically be 40mm (1km) on a 1:25000 map. You can now use the grid lines as a guide to accurately place the north south lines. The spacing should be uniform and set to a value like 1km as these lines provide the user with a "scale" across the map. Remember that there is no need to have the GIS grid on your final map. If the position of the lines doesn't fall exactly where you would like them, reduce the value of the "Grid distance" and use intermediate lines.
Fieldwork The topographic maps which are used as the base for most rogaine maps will always have errors and omissions. They can be more than 30 years old. The "cultural" features (roads, buildings, dams etc) are the most obvious ones you will find to be incorrect. Before you start any serious placement of controls, it is a good idea to at least get the roads and buildings shown correctly. The tools available to do this are the traditional mapping board and the GPS. The Mapping Board. Mapping boards in various forms have been used by orienteering mapers for many years. Where they use them to draw a complete map in colour, we only need to record corrections to an existing map. The board I use is a sheet of 16 gauge aluminium, 32cm x 28cm. A simple compass is screwed to one corner. Print the section of the map where you want to work on an A4 sheet and sticky tape this to the board. Now cover the map with a sheet of "mylar" (polyester) drafting film. Mylar has two important properties. It is dimensionally stable and you can draw on it with a hard pencil. Use at least a 4H. Anchor the pencil to the board with a cord. You will lose it in the first hour otherwise. Drill a hole in a hard rubber eraser and tie this with another cord to your shirt pocket. The other thing you need is a romer with scales in metres. Draw crosses on the mylar at the intersection of the grid lines. Rotate the compass housing so that north on the housing is parallel to the magnetic north lines on the map. Fix a plain sheet of paper to the other side of the board. Use this to record your notes about things like GPS waypoints and track logs. The GPS The most simple use for the GPS is to find out where you are. Read the coordinates and then use your romer and pencil to put a dot on the mylar on your mapping board. Do this a few times in some moderately complex terrain and you will soon find out just how inaccurate not only the cultural features can be but also the contours and watercourses on topographic maps. The good news is that it is easy to do something about it. GPS Basics. The first time you use your GPS you need to check some basic settings. Select "Main Menu / Setup Menu / Navigation" See that ... 1. "Position Format" is "UTM/UPS" 2. "Map Datum" matches your map. For the 1st and 2nd edition NSW maps this is Australian Geodetic 1966. Later editions use the “Geocentric Datum of Australia 1994”. For more information on this subject go to “http://www.lands.nsw.gov.au/survey_maps/geodesy/gda” . 3. "Units" are Metric. The accuracy of a GPS like the Garmin 12 is about 10m horizontally. Later models will give you 3m. The “GPS” elevation reading will tell you if you are at Penrith or Blackheath or half way in between but that's about all. Models with barometer altimeters give 5m accuracy. The 10m horizontal accuracy fits in well with the common rogaining map scale of 1:25000 where 1mm on the map is 25m. The accuracy of your GPS will be reduced by tree cover and hills that block the view of the satellites. If you know you are going to be working in a deep valley with tree cover it is worth picking a time to go there when there is a favourable satellite pattern. These patterns can be obtained from the web. Try http://www.geocities.com/kiwi_36_nz/alm2pos/alm2pos.htm. Plotting Point Features by GPS. Point features are easily plotted. Just stand beside them and record a Way Point on the GPS. You can also read off the coordinates and draw the feature on your map board using your romer and pencil. Plotting Linear Features by GPS. Any linear feature such as a road, track or watercourse that you are able to walk or drive along can be placed on your map. The steps in the process are ... 1. "Walk" the GPS along the feature with "Track Logging" activated. 2. Download the data to your computer. 3. Process the data to create an OCAD image. 4. Draw the feature.
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Making a Rogaine Map - NSW Rogaining Association

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