MapAreas for DMAP (version 0.4)
(C) David Corke, 2000
USE RESTRICTIONS
This program may be distributed freely for private use by individuals. It may not be incorporated into other programs or used or sold commercially. There are no guarantees, express or implied, that it will do what it says it does or what you want it to do.
ACKNOWLEDGEMENT
Dr John Rostron of University of east London (J.Rostron@uel.ac.uk) supplied the algorithms for calculating map areas.
SET-UP
There is no fancy set-up program supplied.
Use Windows Explorer or File Manager to copy mapareas.exe into your C:\program file-folder.
MapAreas was created with an early version of VisualBasic. It requires VRRUN200.dll in your C:\windows\system folder. New versions of Windows do not have this version of VBRUN. VBRUN200.dll is supplied in case you need to copy it to your system folder
PURPOSE
The purpose of this program is to calculate the perimeter lengths and sizes of areas defined in standard DMAP boundary files. It also calculates the lengths of lines defined by non-closed series of grid-references in these files.
BOUNDARY FILES
Before using this program you need a standard DMAP boundary (*.bdy) file supplied with your copy of DMAP or created using DIGITISER for DMAP. It can also be created using any word-processor so long as the file is a text file containing grid-references or other co-ordinates using the format defined for DMAP (see the DMAP instruction manual).
USUABLE GRID REFERENCE STYLES
This BETA version of MapAreas can work with the following co-ordinate systems:
Do not mix different levels of grid reference precision or different styles of grid references within one segment. This will produce erroneous results for the segment concerned. MapAreas will issue a warning with the printed result.
British or Irish OS grid refs in any of the following formats.
TQ59, TQ5293, TQ524937, etc [any level of precision of 10km sq or better is accepted]
51/59, 51/5293, 51/524937, etc [any level of precision of 10km sq or better is accepted]
5519, 552193, 55241937, etc [any level of precision of 10km sq or better is accepted]
TQ59E, 51/59E, [tetrad references using the DINTY system]
TQ59NW, 51/59NW, [5km sq references]
F12, H1234 (Irish, single letter references, any level of precision of 10km sq or better is accepted)
Obviously the higher the level of precision of the references (i.e. length of grid-reference) and the greater the number that define a complex shape the more accurate the calculated areas and perimeter lengths will be.
UTM [Universal Transverse Mercator] references in style 30UVF123456 work within a single zone but not across a compensation zone.
Grid reference systems specific to other countries should work if they are entirely numeric but probably not if alphanumeric (unless they use a system exactly like the British or Irish alphanumeric system)
Latitude/longitide co-ordinates work when boundaries are defined by pairs of co-ordinates which are quite close together (as is normal in a .BDY file). They produce erroneous results if the area is large with big gaps between the pairs of co-ordinates. There is mo warning issued when this problem is encountered by MapAreas: be careful!
General co-ordinates in the format: 1.23,-99.5 are accepted
and MapAreas assumes that these are co-ordinates measured in kilometres unless you set the co-ordinate scaling to some other value. Resetting these scales can (for example) make MapAreas work with the French Grades system of co-ordinates where the eastings values are to a different scale than the northings.
USING THE PROGRAM
Once MapAreas is running, use the drive, directory and file boxes to locate the BDY file you want to work with and double click the file.
Assuming you are working with British grid references (and thus do not need to reset the scales) just click "Calculate Areas" and the program will work through the selected file and display a result for each segment of the boundary file.
SEGMENTS
"Segments" are a consecutive series of grid references terminated by "-1" that define an outline of an area (e.g. an island) or a line (e.g. a river). Closed areas are recognised because the first and last grid-references are the same.
LABELLING SEGMENTS
It is helpful to label each segment in the file as follows:
{name of the segment inside curly brackets}
This name will be used to label the results of the calculation for the segment that follows it. If there is no such label the first grid reference will be given to identify the segment, or the previous segment’s label.
Words that are not in curly brackets (or anything else not recognised as a grid reference) will be ignored in the calculation. This means that controls such as DOTTED or COLOUROFF do not have to be edited out of your DMAP BDY files for use with MapAreas.
SAVING RESULTS
I suggest you test each file on screen only. Assuming the results are satisfactory, run the program again with the option to send the results to disk [and/or printer] turned on. Disk files are more useful than printed output as they can be read directly into spreadsheets (eg EXCEL) or word processors (eg WORD) for further calculations or formatting. The printed output direct from MapAreas is very crude.
WARNINGS
This is a BETA version not yet fully tested. There are very few safeguards to check the entries you make. It is up to you to be careful. If you select a file for output that already exists the output will be added to the end of the file not replace the existing file.
FEEDBACK REQUEST
Any feed back on MapAreas would be most welcome contact DavidCorke@aol.com or by post to David Corke Tye Green House Wimbish Saffron Walden Essex CB10 2XE.
Anyone expressing an interest will be informed when an improved version is available.
DMAP
If you wish to learn more about DMAP or Digitiser for DMAP see the DMAP website at www.dmap.co.uk or contact Dr Alan Morton, Blackthorn Cottage, Chawridge Lane, Winkfield, Windsor SL4 4QR