|A GlobeCs ismertetője (angolul)||Short Manual to GlobeCs|
GlobeCs v3 - What is it?
It is the 3D vector graph of the globe, 3rd version. The globe is turnable, the display is zoomable and scrollable. Features to select view point, show the long-range fly path, put on the grid, crosshair, save the map, etc. Grey, auto scroll, transparent options.
Installation and use, legal status
Put files in the following directories: \APP\GLOBECS3.OPA, \OPD\GLOBECS.ODB, and with Psion-I (English version) install the OPA. It's all. I hope the menu is self-explanatory enough.
GlobeCs is a Public Domain, if you use it, or its parts in your own programs, please credit me. Use it as is, there are no registration and support for.
Psion3a (but I guess it runs on 3c and Siena too). Needs approx. 30-40 kB memory to run, plus the PIC size, which depends on globe radius and the use of grey (3.2-102 kB). It works on PC emulator without problems too (10-40 times quicker).
Menu short description
zoom In - increase globe radius by 40 until 360 pixels, redraw
zoom Out - decrease globe radius by 40 until 80 pixels, redraw
globe Radius - choose radius in range 80-360 pixels, default is 120
move to North by ... - move with the current step value, redraw
move to East by ...
move to South by ...
move to West by ...
Jump to co-ordinates - input longitude and latitude in degrees, South and West is negative, redraw
Fly - displays the shortest fly path between two cities, input departure and destination city names
Grid on - puts the meridians and circles of latitude with step
crossHair on - puts vertical+horizontal lines on the globe visible centre (view point)
greY on/off - toggle the use of grey plane, default is on, redraw
Transparent on/off - glass globe, hidden continents on the other side are visible too
aUtoscroll on/off - during map plot the display window follows the plotting area
reDraw map - manual request for redraw e.g. after change radius
save Map - saves the actual map in \PIC\ directory as picture
change steP (for grid or move viewpoint) - possible steps: 1,2,...30,45 degrees, default is 15
eXit - quit program
About - short message
Data representation and vectorization
The coastline of continents and islands and some big lakes is given like ODB file in binary form. Each point of the coastline represented by two integers (absolute longitude and latitude in degrees, West and South is negative), the end of a polyline indicated by two zeros. The usual step between the break-points is not greater then 7 degree (i.e. 3 bit, in this way it would be possible to save components of a relative vector with their signs in 1 byte, but the unpacking is a surplus time consuming procedure).
The data order, and so the plotting sequence of continents is the following: Africa, Europe, Asia, South America, North America, Australia and Antarctic (that's why the display is blank for a long, if the view point is e.g. on the West coast of USA or in New Zealand).
Some attempt made to keep continuos line even in case of near islands. In this sense I am proud of the Sumatra, Java and Lesser Sundaes, the British-Irish Islands as well as US-Canada Great Lakes but the Philippines turned out not very well. Presently the file consists more than 1500 points. By now some more or less islands in Arctic Ocean are missing, it means 300-400 additional points.
Computation and speed
The rotation of globe and calculation of visible/hidden points requires much trigonometry beyond the spherical-Cartesian transformation. For speed-up the code I used the following tricks:
The initial preparation of SIN table and dark background takes 7 sec. The time of plot recently is approx. 50 sec, does not depend on the globe size, and the view point. If auto scroll selected, the time is longer, about 1 min, and slightly depends on radius and view point. The plot time of grid strongly varies on step value.
The SIN normalization factor 1024 comes from the following considerations:
Bugs and known issues
In GlobeCs v1 fixed a small bug in saved map filename (sign of longitude part, i.e. E or W sometimes was wrong).
Known symptom is when changing the radius and then choosing "Grid on" the grid is drawn in the wrong size. This is not a bug: first you have to redraw the map. It would be easy to initiate automatic redraw, but due to plot time I decided to allow change more than one settings (e.g. step, radius, auto scroll) before next redraw.
D. Rushall's Solun 3 in registered version is able to show the 3D globe map. I have seen only its display hard copy, but as I understood, that globe is fixed size. Am I wrong? J. McAleey's W2 program does for 3D map the daylight/dark screen.