MILEMARK.TXT INTERSTATE MILEMARKERS =========================================================================== Document version: 8.5.3 Document dated: 30 Aug 2002 (previous was 30 Mar 99) Author(s): Bob Bruninga, WB4APR ABSTRACT MILEMARK.TXT How to use Interstate milemarkers in APRS and APRStt ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Mile markers are the universal mobile radio position location system. Everyone from CB to ham radio uses them. By adding this feature to APRS, you can easily locate someone simply by reference to their Mile Mark. APRSdos uses a data base stored in SYSTEM\MILEMARK.DAT. Each line in the file represents a straight line segment between two mile markers. APRSdos uses these to interpolate any mile marker inbetween by interpolation. Only California is excluded because it has no state-wide MM system. Interestingly, the MileMark.DAT file does not need both LAT and LONG for each mile mark. If the road is north/south, then you only need a LAT. If the road is east/west, then it only needs a LON since the location of the road itself gives the other dimesnion. The Command in APRSdos is MILE-MARKER-VA95-114 for example. This will cause APRSdos to plot a horizontal line at the approximate latitude of the mile marker 114 on interstate I-95 in Virginia. The intersection of that line with the interstate on the map is the location of mile marker 114. If you entered M-M-VA81-56, then APRSdos would plot a vertical longitude line intersecting that interstate approximately where MM 56 should be. Entries in the MILEMARK.DAT file are of the form: VA95,NS,M1,L1,M2,L2 or VA81,EW,M1,L1,M2,L2 Where the first field identifies the interstate, and the next field indicates either NS or EW for north/south roads or east/west roads. This field tells APRSdos whether to use LAT or LONG in the interpolation. Thus it is trivial to build this file for your area. Simply enter the mile marker number and its LAT or LONG depending on whether the road is more vertical or horizontal. Although many entries may be sequential in that the end MM of one line is the starting MM of the next, this is NOT necessarily the case. For example, to encode the following road, *M9 / M1 M5 / *------------------------* \ *------------------------* / M6 M9 / *M3 I would enter the E/W road as two entries, one for M1 to M5 and another for M6 to M9, and not bother with the short jag between M5 and M6. Similarly, the mile marks from M3 to M9 can be done with ONE line segment because from M3 all the way to M5, the slope of the road is the same such that the amount of LAT increase per mile is the SAME whether it is going NE or NW. A milemarker requested between M5 and M6 *will* still get interpolated as being a little beyond M5 but it will only be slightly off. So, concentrate on building the data for the long straight stretches and dont worry about the nooks and crannies. I only used 9 entries for the 400 miles of I-40 through the length of Tennessee.. I have built the entire database for all states with mileage exits since I could get the data from a Highway map, but I need help in those states that dont have mileage exits. Here are the states I cannot do just from maps. I need LAT/LONG of the key mile markers: MA, ME, NH, PA, and NY interstates 81, 88, and 390 In CT, still need I395 at route 2 Norwich I395 at rt 138 or 164 I395 at Mass State line I95 at RI state line Note, in NY, the I-87 portion of the NY State Throughway is called NYST to distinguish if from NY87 where mile mark 0 restarts. If you are driving in these states and can write down the mileage of the key mile markers (those that mark turning points between long straight segments) please send them to me. However, please do not encumber me with lots of little segments. We are just trying to get a rough translation between mile marker and position. The program MM-CHECK.BAS will scan the file to make sure it has all the data elements in the right place. APRS-Touch-Tone MILE MARKS USING THE FILE MM.ALL ------------------------------------------------ Mile marks have also been added to APRStt so that touch-tone users may place them selves on the map anywhere with only a few digit entry. But since this is a complete position, the MILEMARK.DAT file had to be re- done to add LAT and LONG to every reference point. This file is MM.ALL which we will try to maintain as the whole-USA file. This file is then trimmed down by each APRStt SYSOP to match local needs and saved in the local file named MM.DAT (with backup copy named MM.SS for each state or local area). In APRStt, the DTMF entry MMRD#nn will place a station on the map in the vicinity of mile mark nn on road RD. Depending on proximity to other states, the name of the road "RD" can either include the state two letter abbreviation or not depending on whether ambiguities would result on state borders. For example: The entry MD50,0,43,LA1,LO1,LA2,LO2 covers the stretch of Maryland Route 50 starting at mile mark 0 and going to mile mark 43. Since APRStt is a local program, it only needs entry for roads within RF range of APRStt. So only copy over the needed entries from the MM.ALL file to your local MM.DAT file. If there are no adjacent state ambiguities, you may also remove the state abbreviation from the entry to save keystrokes for the APRStt user. BUT if you need to retain the STATE abbreviation to resolve borderline ambiguities, you must convert them to the hashed equivalent DTMF numerical digit. In my case, "MD50" becomes "6350". If you make refinements to either MILEMARK.DAT or MM.ALL, please let me know so I can update the master files. NOTE: MILEMARK.DAT was only dependent on the SLOPE of the road between the two end mile-marks, and so zig-zag roads going back and forth but with complemntary angles still only needed the start and end points. But when converting to MM.ALL, each straight line approximation of the highway needs to have its own line segment. When I converted MILEMARK. DAT to MM.ALL, I did not have time to edit in the new line segments needed to cover all such segments. So as you customize it for your area, be sure to check for this and add points as needed. de WB4APR, Bob