MAPS100K.TXT BUILDING 100K MAPS =========================================================================== Document version: 8.3.5 Document dated: 10 Mar 99 Author(s): Bob Bruninga, WB4APR ABSTRACT MAPS100K.TXT Final notes on building 100K maps. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ The MK100k3.exe program written by KB4XF, Jack Cavanagh, has made it possible for anyone with the $32 USGS CD ROM (optional format!) or files downloaded from the internet for their area to make street level maps up to 9 at a time. See my MAPS-CD.txt file and the details in MK100k3.txt that comes with the program. Your effeciency at using this program will be the result of how accurately you estimate the density of roads in a given area. The objective is to have your maps come out close to 3000 points. You also want your maps to be reasonably matched to the 15 x 15 minute cells of the CD data. Below are three side-by-side 15 minute cells. In my area with a latitude of 40 degrees, the cells are taller than they are wide. Combined with the wide 3x4 aspect ratio of the PC screen results in just about double the number of maps vertically relative to the horizontal width. The dotted horizontal line in the center just highlights this fact that the cells are twice as tall as they are wide relative to an APRS map. |<--- 15 min--->| ------------------------------------------------- --- | | | | : | | | | : | c | c | c | : | x | | x | : | | | | : |- - - - - - - -|- - - - - - - -|- - - - - - - -| 15 min | | | | : | | | | : | c | c | c | : | | | | : | | | | : ------------------------------------------------- --- x x VERY SPARSE: Make TWO +4.2 mile maps per 15 minute cell, one at the top, and one at the bottom using the centers C. Will NOT work for Maryland since it results in about 4000 pts each. Should work in the west... NORMAL EAST COAST RURAL: Make EIGHT +2.1 mile maps, FOUR around the top, four around the bottom center. In these cases the centers c are 4 minutes below the top and above the bottom of the 15 minute cells. They are in the middle horizonatlly at 7.5 minutes from either edge. CITIES/RESIDENTIAL: Make NINE +1.25 mile maps top and bottom using the same centers C. But place them 3.75 minutes in from the top and bottom. These first three techniques use the 1, 4 or 9 map methods in the MK100K program, but the 1 map is too big and the 4 map method is too small for our rural areas. The following method gives you a good technique midway between these two. SPARSE RURAL: Make FOUR +3.3 mile maps centered on the X's above. These four map groups will take one-and-a-half 15 minute cells wide and 3/4 cell tall. This means that you can do this SIX times for each grouping of 3 cells wide by 3 cells tall. By making them 3.3 mile maps, there is no overlap into adjacent cells. The centers at X are 1.75 minutes in from the left or right edge, and 1 minute up or down from the nearby horizontal edge or center line.. ALways run MAPFIX and TASK-SCRUNCH at the 1.2 ratio just to remove redundant points. If you are still at about 3500, you can still get under 3000 points by stepping through every point in the map and deleting unnecessary points. CITIES: In dense city block areas with straight roads, you can drastically remove points by redrawing many parallel blocks as intersecting long straight lines. Consider an area of 10 x 10 square blocks. APRS can draw that grid with 20 lines, or a total of 40 points. From the CD, this area will be made up of TWO points AT EVERY INTERSECTION or 200 points. To clean up this mess, simply draw new YELLOW roads over the grid area, then HOOK and delete points. Since the YELLOW roads are drawn on top last, and the HOOK function selects the FIRST roads in the file, it will always find the original CD roads to DELETE. Also drawing your own straight roads is probably closer to reality than the jagged and crooked blocks drawn from the CD due to truncation errors. When done, do an EDIT-CHANGE to change the color back to gray. If you accidentally delete the wrong road, you can always TASK-OVERLAY the original map file on top of where you are working to see the original file. (This is why you should never delte the original file, or SAVE over top of it..) UNEVEN DENSITY: Many times a group-of-four maps will come out with about 1200 or fewer points in some of the maps and then a lot more points in one or two that have a small town. Here is how I combine these maps. The HIGH density maps will remain as is. But take one of the other 4 maps and use it as a starting point. CHANGE-CENTER to the center of the 4-map area, CHANGE-RANGE to double the original size. Now you have a 4 times larger map that you can TASK-IMPORT the other sparse maps into. These retain the original full detail. Now for the maps that dont fit because they are too dense, simply TASK-OVERLAY and use the EDIT-NEW and EDIT-ADD commands to sketch in the main features of the missing map. If it is a distinct town, simply use the color 6 to draw in the town limits and then only add the major roads. The result is a 4-times larger map which can now take the place of the multiple sparse maps, and includes enough detail of the dense area. Of course as you zoom into the dense area, APRS will load and use the original dense map of that area too. The advantage of this techniqe is that you will have fewer maps in the MAPLIST and you will have LARGER maps where density is less. I sketch in the dense map rather than IMPORTING just the 10, 12, and 4 colors since by importing you end up with about 5 times as many points per road as you need at that larger scale. It takes longer to delete them than it does to sketch over them. FINAL STEPS FOR A SEAMLESS MAP SYSTEM: Using the techniques above, you will have a map system of total coverage, but APRS will not display the maps if you happen to zoom in on an edge. You can avoid this problem and make a completely seamless map system with a lot more work as using a combination of the following two approaches: BRUTE FORCE: This method takes the existing grid of adjacent maps and creates a completely new grid of maps whose centers are at the CORNERS of the original grid of maps. The process uses MAPFIX and the alt-IMPORT command to import streets from adjacent maps into each of these new maps. This covers the corners of the original grid, but you still have no overlap at the top and bottom centers of the original grids. This requires yet another grid offset by 1/2 mile up and down. This process will result in trippling the original number of maps... JOINING SMALLER MAPS: This method looks for adjacent maps that are relatively small 700 to 1500 points that can be combined with others and still stay below the 3000 limit. Look for low desnity areas that can be combined to make a larger maps. Similarly, take dense towns and make a new smaller map right at the center. Use the MAPFIX TASK-IMPORT and TASK-TRIM commands. OVERLAING INTO A BIGGERMAP: Always extract all streets for an area. Although this gives you LOTS of maps, at least you have the data. After you have all the small maps, then make the larger 8 mile maps by selectively using the TASK-OVERLAY command to show you where all the roads are. THen simply use the EDIT-NEW command to sketch over the important roads and add them to the 8 mile map. You could also do a TASK-IMPORT of just the color 10, 12 and 4 roads, but you will get a LOT more points than are needed at this scale. Removing those redundant points will take as log as just drawing them in the first place. Look for winding roads or long straight ones that locals will recognize. Draw in only the detail needed at this scale. Do not try to get EVERY point, just a good approximation of these thoroughfares, since this larger map will only be visible at the larger scale. The exact detail will appear as the user zooms in. Only a few of these thoroughfares are needed to give the user the visual structure of sub-divisions and known landmarks. All of these methods use either the IMPORT or the OVERLAY feature of MAPFIX. Actually these two commands are really the same routine. The IMPORT brings points INTO the current map under construction, whereas the OVERLAY only draws them on the existing screen so you can SEE the points temporarily. This is so you can add more features to your working map by drawing over selected features in the OVERLAYED map (without having to IMPORT them ALL). Once you have given the file name for either command, you can re-use the same map over and over again with a single keystroke. This is particularly valuable with the Overlay command. To control the points that you want to IMPORT, the WHITE box representing the map CENTER and RANGE is a very powerful tool. The IMPORT function will ONLY import points that will fit INSIDE the white BOX where ever it is. You may move the box edges around anywhere you want with the CHANGE-CENTER and CHANGE-RANGE command. When IMPORTING adjacent maps where there is significant overlap, use this technique: 1) Load the first map 2) TASK-OVERLAY the next map to see where it is going to fall 3) use the CHANGE-CENTER and CHANGE-RANGE to move the white box so that one of its edges makes a clean line just inside the existing map edge 4) Now hit TASK-IMPORT and the second map comes in just up to the white line with minimal overlap. Now there will only be a few streets that duplicate and they can be removed using the FIND and DELETE commands. SUMMARY: Once you have finished generating your original 100k map grid, and can see the general density of the streets throughout the city or town, you can use the above techniques to build your maps into a seamless system of maps that in most cases is transparent to the user. This probably takes as long or longer than the original MK100k process, but it is ESSENTIAL for user satisfaction.