============================================================ Quick Basic programs for calculating Microsoft Flight Simulator coordinates in the United Kingdom. ============================================================ The other-wise excellent Microsoft Aircraft and Scenery Designer program (for use with Flight Simulator 4.0) has a problem with coordinates. An option to use latitude and longitude is offered, but does not work in the United Kingdom area (perhaps the reason why it is not officially on sale here!). This is a bit of a problem if, like me, you wish to improve areas of the fairly barren UK scenery. Microsoft Flight Simulator is still, to my mind, one of the finest items of software available for the PC. I have never really found computer games very satisfying, but FS (without warfare) kept drawing me back. After finding I could do consistent landings (without any idea what the flaps were for) I started to wonder what the real thing was like. Eight months and 4000 quid later, I now know. FS was not really very useful in practicing general handling or visual navigation, but now I am thinking of doing the IMC rating, its radio-nav aspects have come into their own. I could practice in the USA, but would prefer to fly in the UK (I'll probably never actually fly outside it). So I need to be able to improve my local flying area scenery using ASD. When I first read about it, I hoped that the manual would have data on the coordinate system and that I would be able to compile numeric files into scenery. Unfortunately, you have to create scenery in the ASD itself and there is no information on the coords base. Finding that the Lat/Long option was rubbish was another blow and the CAA charts don't have an FS grid overlay (strange omission!). I am a hydrographic surveyor and fairly familiar with different coordinate systems, so I knocked together a basic Lat/Long to FS program using a few points known in both systems. It didn't work. After a week of exploring other avenues, I discovered that one of the points I used - Southampton VOR - is miles out of position in the FS world, almost coincident with the Seaford VOR! FS-TEST acts as an integrity check program to weed out any rogues. Things are not perfect on the scenery disk, but these programs seem to be correct to within about a hundred metres. For the best accuracy, you should select points to give a roughly equilateral triangle, containing the area in which you wish to make conversions. Deviation angles between the grids are shown to a decimal degree, but aerodromes are probably best skewed to give the correct runway orientations (as runways are quoted in magnetic this will not be much). ============================================================ FS-L2F allows on-screen conversion from Latitude/Longitude to Microsoft Flight Simulator coordinates in the United Kingdom area, primarily for use with the Aircraft and Scenery Designer program. The Lat/Long coords are converted to Ordinance Survey grid coordinates (using an algorithm I was given some time ago by Dr Chris Davis of UWIST) and then converted to FS grid by a transform using three points (known in both OS and FS coords), fairly widely spaced around the area in which conversions are required. These must be edited into the file FS-OS.DAT. Input files (for When compiled with Quick Basic the usage is:- >FS-L2F [/P] [/O [resultfile]] [/I inputfile] /P adds printer output /O adds file output (defaults to FS-L2F.RES) /I takes LatLong data from inputfile Input files (for batch use) must be lines of text in the form - "N5143.50, W00315.70". ============================================================ FS-O2F is a sub-set of FS-L2F which allows on-screen conversion from Ordinance Survey grid to Microsoft Flight Simulator coordinates in the United Kingdom area. The usage is the same as FS-L2F, except that any input file should contain `easting, northing' (eg "319428, 171973"). ============================================================ FS-GRID uses a reverse transform (again with data from the file FS-OS.DAT) to create a file of the FS grid intersections of a given rectangle in terms of OS coordinates. These could be plotted onto an OS map (or an overlay) to allow you to read off FS coordinates directly. ============================================================ FS-OS.DAT is required by FS-L2F, FS-O2F and FS-GRID. It is a list of points defined in FS coords and OS coords. Choose three well-spaced points surrounding the area in which you require conversions. Mark the three chosen with a `*' in first position on name line. To add more points to this list, you can get OS coordinates from published Lat/Long (convert with FS-L2F) or OS maps, and FS from Flight Simulator data sheets or slewing to recognizable places. Watch out for obviously duff FS coordinates (Southampton VOR is very wrong). In the Flight Simulator world VORs are set on integer coordinates, so perhaps runway crossings may be the best points to use. ============================================================ FS-TEST tests the integrity of the FS/OS coordinate data in the FS-OS.DAT file by finding the distance between all pairs of points in both FS and OS terms and finding the ratio between them. Any ratios which stray from the mean scale (268 metres per FS unit) are marked. Results are sent to file FS-OS.ERR. ============================================================ FS-L2F.EXE is the compiled version of FS-L2F.BAS. ============================================================ While I am happy to allow free use and modification of these programs, I retain the copyright. ============================================================ Andy Zienkiewicz Cardiff 0222 794329 February 1991 ============================================================