OCAD is a program which was created expressly for creating orienteering maps, though in it's latest release (v6.02), it is quite capable for general purpose cartography. You can find information at http://www.ocad.com.
At the moment, I can provide basemaps in either OCAD version 5 or version 6. The newer version has some nice features, like the ability to work in real-world coordinates (e.g. UTM), greater flexibility in creating symbology, and a larger page size. However, files in version 6 are about twice as large as in version 5 due to an adoption of a 32-bit coordinate space (from 16-bit before). OCAD is a requires Microsoft Windows to run. Version 5 will run under Windows 3.1 or higher. Version 6 requires Windows 95 or NT.
Your basemap may have been compressed to allow it to fit on a floppy disk or to make it faster for internet downloading. If so, instead of finding a file with the .ocd extension, you may find a self-extracting zip archive, with the .exe extension. Copy this file onto your hard disk, to the directory from which you plan to work on this map. Executing this file (type it's name -without the ".exe" - at the DOS prompt) will extract the OCAD file. Alternatively, your file may have the ".zip" extension, in which case you will need to use an application, such as WinZip to decompress the file.
On the plotted version of your basemap you will see a grid of blue lines that correspond exactly with a grid in the OCAD basemap. You should use this grid to keep your work in register (before you do anything else on your field notes, copy that grid!). This grid may be rotated to correspond with magnetic north, or it may correspond to the Universal Transverse Mercator coordinate system (your choice). Since OCAD 6 now supports "real world" coordinates, the basemaps I deliver in OCAD 6 format will be registered, usually within ten meters, to the UTM coordinate system. This enables two possibilities: merging map data from other sources; and using OCAD 6's ability to work with a GPS systems.
The basemaps are already accurately rotated in OCAD and on the mylar plots to have magnetic north at the top. I use a program from the USGS called GeoMag, which can estimate magnetic north on any point on the globe at any point in time (well, between about 1980 and 2000), to within a tenth of a degree. Since this measure is taken with reference to true north, and the internal coordinate system of the map is UTM coordinates, I use a program called UTMS, also from the USGS, to calculate the discrepancy between the UTM grid true north. Subtracting this UTM convergence from the magnetic declination provides a rotation value for the map, which is what I use.
The grid is on your basemap is usually 500 meter (250 meter on a 1:5,000 basemap), and very accurate. The scale on the plotted copies of your basemap should be pretty accurate, but it is not perfect. Likewise, any copies of the basemap that you print yourself from OCAD will probably not be accurate. In each case however, the grid provides a perfect link with real world scale. Since all work is kept registered by using the grid, there should be no problem with distortion creeping into the process. This is why it is crucially important that the grid be copied onto all field work from the basemap. Do not rely upon matching feature-to-feature.
All this said, don't take my word for it that the scale and rotation are accurate! I can make mistakes! You should check that the magnetic north is accurate, just as you would with a basemap from anyone else, and you should check that the scale appears accurate, both in the OCAD basemap, and on the mylar plots.
OCAD organizes the drawing by having all symbols defined in a symbol library and all colors defined in a color list. I have defined a set of basemap symbols that exist in parallel with the standard IOF symbols. Whereas the predefined IOF symbols are numbered beginning with 101.0, the basemap symbols occupy the numerical range of 1.0 to 63.0. Also, the basemap colors are separate from the IOF map colors, and because of their order in the color list, draw before (or underneath) the regular colors. The basemap colors are muted (normally about 50% of the standard colors) so that they can be visually distinguished from "real" map features. The basemap symbols are located in a section of the symbol palette below the other symbols, and are identifiable by their gray background.
As wonderful as it might be to map in OCAD, directly in the field, for most of us this is not an option yet. But having the basemap in OCAD can still be very valuable because it can save substantially in duplicated drafting effort - if something is accurately drawn on the basemap, it is unnecessary to draw it again. The actual usefulness of having a basemap in digital form depends upon the circumstances of the particular area that you are mapping. The more complete and accurate the basemap, the more useful having it in OCAD form will be. In particular, areas with a lot of cultural detail (buildings, roads, fences, etc) will benefit by time saved not drafting features that are already recorded accurately in the basemap. I would not recommend making direct use of the basemap contours since properly field checked contours will always be changed (sometimes subtly) from the basemap.
A Suggested Technique One technique I would offer to the field checker to use in the field is as follows: If you wish to copy a basemapped feature to the finished map, trace it in a normally unused color (e.g. purple). This is the "signal" to the draftsman to "copy-up" this feature (or portion thereof) from the basemap to the IOF symbols. In the case of a feature such as a trail, be sure to signify (by label or other convention) which type of trail it is. Other features are recorded in the field notes in the usual way (drawing them with variously colored pencils). Any basemap features which are not traced are simply ignored in the copy-up phase.
Drafting On An OCAD Basemap In OCAD 5, the field notes may be either scanned and placed in the drawing as a template, or traced on a digitizing tablet. OCAD 6 no longer supports the use of digitizing tablets, so the field work must be scanned. Using a scanned template has the advantage of direct visual feedback, at the expense of some drafting efficiency. With the OCAD basemap, you have the option to reassign features from the basemap symbol to an IOF symbol. This is, for practical purposes, the same as if you copied the elements up from the basemap to the finished map, except that it is a perfect copy, and is much less work! It makes sense to do this copy-up work first (e.g. wherever the field notes are purple), followed by deleting the remainder of the basemap which is not being copied into the final map (you should delete the basemap symbols and extract them to a separate file, in case you need to pull them back in later). In OCAD 6, instead of deleting/extracting the unused basemap symbols, you can simply hide them. Once you've finished the copy-up phase for a particular section of the map, you can load in your scanned template(s) and draw from the new field work.
Good luck!
-- Pat Dunlavey