README.MAP 5.9c            HOW TO MAKE YOUR OWN MAPS


OVERVIEW:  My general philosophy is to keep maps simple so that APRS will run
quickly on any PC machine, including 8088 laptops, and so that maps can be
made by anyone.  I had wanted to do APRS for years, but could not get any
commercial MAP software company to release map info to the amateur community
without royalty and ownership problems.  I finally bit-the-bullet and decided
to come up with a simple graphical technique that anyone could use and
understand.  For these reasons, APRS limits the number of points to 1500 and
the number of labels to 99; any more detail on one map just clutters the
screen and makes it difficult to see all the APRS stations.  This does NOT
limit overall map resolution, however, since APRS overlays maps of increasing
resolution as you zoom in. To see the typical street level ability of APRS,
Zoom in to the 1 mile range in the center of Idaho Falls, Idaho.


MAP COMMANDS:  Before getting into the detail of how to build APRS maps, use
some of the MAP-MENU commands in APRS to become familiar with the APRS map
structure.  You will see how maps are overlayed in a hierarchical manner
from the whole world, down to increasing detail.  This hierarchical list
is established in the MAPLIST.xxx file which tells APRS the names of all the
maps available to it, their size, and the location of their center.  APRS
constantly checks the location of the cursor relative to this list to decide
when to load a new map.  The following MAP-MENU commands will help you see
this hierarchical structure:

  B - Borders:  Shows borders of all MAPS in the MAPLIST.apr file.  To see
      more and more borders, use the F3 key to soom into further detail.
      If a map border appears, but the map does not come up in APRS, then the
      MAP file is missing.  If the Map file exists but the borders do not show
      up, then the file is not listed in the MAPLIST.apr file.

  H - Hierarchy:  This is an improvement on the BORDERS command since it
      colors in the maps in the same sequence as they are listed in the
      MAPLIST.xxx file.  The overlapping colors show the effect of the
      sequence of this list. If you see any border that is not colored in with
      its own color, then it will be invisible to APRS, since it is overlapped
      by other maps of the same area following it in the MAPLIST.xxx file.  To
      correct this problem, move it later in the list than the overlapping map.
    
  A - ALTmap:  Displays the map UNDER the current map.  Since APRS always uses
      the latest map in the MAPLIST.APR file that meets the current cursor
      location and screen range, areas where maps overlap may sometime be
      obscured.  This command displays the next higher map in the list.

  L - Locks the current map.  This defeats the normal APRS auto-map select
      feature so that you will not get a redraw if your cursor gets over
      on another map during a special event.  This also lets you zoom way
      out to see the actual limits of the data in the map file, even if,
      for some reason, the map border is different than the actual data.

  FILES-ChgMapList - This command under the FILES menu, lets you have multiple
      MAPLIST.xxx files, and to save your favorite one in your CONFIG file.
      This is a significant improvement so that everyone can keep his local
      customized MAPLIST.xxx file separate from the generalized MAPLIST.APR
      distribution file.  This also simplifies the task of the state APRS map
      coordinators.  They can now maintain update to date MAPLIST.xx files for
      their states without ever having to merge them with the normal .APR
      listings, since they can be swapped out with a single key stroke.


METHODS FOR MAKING APRS MAPS

     There are several methods for making maps depending on the resources
available to the user.

  MANUAL     - Ruler and Pencil method.  Most APRS maps (60+) were done this
               way!  Just use a pencil and home-made template to determine
               X,Y offsets from the origin in the upper left corner of the map.
               Then use a DOS editor to enter the X,Y values into a map file.

  MAPFIX     - This program can edit or modify MAP files.  But free-handing of
               the cursor on the screen is difficult to match real world
               coordinates.  This method is best for sketching in local roads
               on existing maps.

  CD ROM     - MAPFIX can also inport data points from the 1:2,000,000 USGS
               CD ROM of the whole USA; but the resolution is only down to the
               state road level, and 4 to 8 hours of manual filtering is
               required to eliminate redundant point data.  W7KKE has written
               a conversion for the USGS 1:100,000 CD ROM, but says it takes
               days of manual effort to put all the data together into a
               meaningful APRS map, since USGS data is VERY fragmented.

  AUTOCAD    - KG8GE has developed programs for building APRS maps to and from
               AUTOCAD.  See the section at the end of this file.

  DIGITIZER  - MAPFIX can accept input from a digitizer tablet.  This makes
               all points very accurate and is the FASTEST way to inport a
               map.

  GPS REPLAY - This is the easiest way to add detail in your area.  Just drive
               around with your GPS, saving APRS track history files.  Then use
               MAPFIX to overlay these histories onto the screen for easy cursor
               drawing.

Look for the sections below that describe each of these methods.  The manual
method is described first, since it gives you the basic structure of the
APRS maps format.

GENERAL CAUTION:  APRS maps are NOT intended, nor expected to fulfill all map
requirements.  APRS maps are only intended to provide the user with a visual
reference to where things are in a radio network.  Once you see where a station
is, and you want to see what street he is on, or what address block he is in,
you should refer to printed maps of your area or make a higher detail map.  Do
not waste time trying to put too much detail into APRS maps!  Similarly, don't
try to label everything.  Too many labels makes it hard to see callsigns.
Also, while driving along at 60 MPH and 30 second GPS updates, zooming in
below about 8 miles makes the map move so rapidly so that fine detail is not
needed.  I usually stay at the 16 mile scale to see what is comming ahead.
This confirms that in most cases a straight line between intersections is just
as effective as a very detailed curvy map and only takes 2 points vice 20!  So
concentrate on plotting the intersections accurrately; if you want to come
back later and add more detail curves for artistic sake, that is easy to
do with the MAPFIX.bas program.


HOW TO MAKE APRS MAP FILES:   To see what maps are available to the system,
use the MAPS-BORDERS command.  This command draws the boundaries of all map
files and shows you the areas covered by detail maps.  The colors of these
borders are proportional to map size.  Some of these maps are very detail,
and some are just "starter" maps that I have made to give new users in those
areas a basic map outline from which to add their own detail.  If your local
APRS net does not have at least a 64 mile map, please contact me.   It is
also easy to shift the center and detail of maps to highlight your area.  See
the section MORE ABOUT MAPS at the end of this file for info on how to center,
convert and spawn new maps.  Slowly other APRS users are beginning to produce
maps.  Here are some good map makers and state APRS map coordinators.

KA7UUS @ K7BUC.AZ      Tuscon         AZ
KD6MKS                 Silver Lake    CA
W7KKE  @ KA6EYH#nocal  San Francisco  CA did Digitizer and GPS code for MAPFIX
WA4MEJ                 Jaxonville     FL
KD4UYR                 Clearwater     FL
N4FOR                  Savannah       GA
KG0DW & N0YKX & KI0Q   IOWA           IA
KB5YRZ @ N5SSY#METLA   New Orleans    LA
KD1E   @ N8NNN.#SEMI   Michigan       MI
W8VPD                  Michigan UPPER MI
KB8JXO @ W8CQK.#CMH.OH Columbus       OH
W4NMK                  Black Mountain NC
N2FET                  New Jersey     NJ
KD1HA @ KA1RCI.RI      Rhode Island   RI (new england)
WB5DTW                 SanAntonio     TX
N3FKV                  Waco           TX
N4WJQ  @ WA4TFZ.VA     Charlottsville VA
W8KVK                  West Va        VA
W9LZQ                  Onalaska       WI
KU0G   @ KU0G#NWMO.MO  Kansas City    MO


OVERALL APRS MAP FILE FORMAT:  In any map file, the first 8 lines define the
origin and scale.  Comment text is permitted on these first 8 lines after the
initial data value and a comma.  See the example map below for Colorado.  The
remainder of the file just lists X,Y points that form the map features
such as roads and rivers.  To end each such feature and begin another, APRS
uses a 0,0 entry.  The next feature begins with the value of the line color,
followed by the feature name.  At the end of this file, is a 0,-1 which marks
the end of points data, and the beginning of the list of map labels.  See the
COLORADO map example below and the section on map labels.


  
MANUAL DOS TEXT EDITOR METHOD:  Simply use a DOS editor to make a list
of points for APRS to use in drawing line segments.  Note that the coordinates
are listed as X,Y where X is horizontal and Y is vertical.  This is backwards
from the usual order that we list LAT (vert) and LONG (Horizontal), so be sure
to put the horizontal (X) value first. You can use any editor to prepare a map
file.  Simply use a chart that has lat/long references and select an origin
beyond the upper left hand corner of the area you want to cover.  That point is
0,0 and all points are measured from there. (negative numbers are OK if you
later add points behind the origin, but the - is an extra character that slows
down file loading); similarly, an X value of 0 is not permitted since it is used
to indicate separations between the end of one feature and start of another.

MAP SCALE:  Next choose an appropriate scale in pixels-per-degree of longitude
and latitude for the area you want.  Since EGA graphics has a 350/640 pixel
resolution, I have found that 120 pixels per degree (2 pixels per  minute) is
excellent for large state maps.  I used 12 pixels per degree for the whole US.
By keeping the scale number an integer multiple of 60, you avoid any future
roundoff and truncation errors due to ZOOM functions and when converting
points from one map scale to another.  I have used 6,12,24,30,60,120,300,600,
1200, etc.  It takes 1200 pix or more in order to resolve city streets.  If
you use too fine of a scale then you are limited as to how far the map can
extend.  Points with values greater that 999 should be minimized and no values
should be bigger than about 1100 or there is a chance APRS will crash on very
zoomed-in maps.  The further you zoom in, the larger the values become until
you get an overflow error.

MAP RANGE:  Since APRS handles range scales as integer powers of 2, I suggest
making most maps slightly larger than any given power of 2.  This is so that
you can place the cursor in the center of the map, and pretty much see all of
it at once.  If you make the size of your map just under a power of 2, then
you can never see the whole map at that range.  Going down a scale permits
you to see all of the map, but only a smaller portion of it at a time.  To
make it easy to hit the center of a map with the cursor, I usually make my
maps with a range scale about 10% larger than an even power of 2.

MAPLIST.apr:   This file contains the list of all map files available to the
APRS program and decides which map is loaded for every location of the cursor.  
The first 3 lines of the file also contain the default LAT/LONG and Range for
the first map loaded.  The program uses the default LAT/LON to center the
first map each time the program starts up (on unregistered users).  The normal
distribution copy of MAPLIST.APR contains the default coordinates for the
center of the US.  These values are ignored when a saved backup file is
loaded using the FILES-LOAD command, or when a registered user has saved his
default location in his CONFIG file.  So to force APRS to start up at your
location, you can either  1) change the default location in the MAPLIST file,
2) move the cursor to your location and use FILES-SAVE to save a backup file
with you at the center, or 3) if you are a registered user, save a config file.
The MAPLIST.APR default location is also stored in the #1 MAP HOT KEY so that
you can instantly zoom out to the default map (the USA) with a single key
stroke.  This is useful for doing a quick glance at HF mobiles that might be
comming in through a GATEway!

ADDING MAPS:   To add a map to your system, look at the MAPLIST.apr file.  It
contains a list of all maps useable by the system.  There can be multiple
MAPLIST.xxx files.  The MAPLIST.APR file comes with the APRS distribution and
contains all regional, and state maps, plus some representative local maps.
You can either add your map to this file, or add it to any local state lists
that might be available.  Currently there are complete MAPLIST.xxx map files
for many states such as Calif and Ohio.  The MAPLIST.OH file lists over 40
local Ohio maps!

     To add your map, simply add a line that contains the MAPname,
LAT, LONG, MAPrange, and comments.  The LAT/LONG are in decimal degrees and
describe roughly the center of your map.  The MAPrange tells the system to
load this map if the cursor ever falls within this range of the center.
Actually it is a little more complicated.  The given map will not be used until
the cursor location plus the current range scale in all directions fully falls
within the boundaries.  HINT - so that your detail map seems to blend in with
the next larger map, add enough rough features and points to your borders to
surround your fine detail area with crude detail out to MAX Range beyond.
Then when the screen centers on a point near the edge of your fine detail,
your map doesn't just stop but includes crude detail to all edges.

     Currently APRS can only use 140 maps in MAPLIST.apr.  To make room for
new maps, but keep old ones handy for later use, You can place a (*) at the
beginning of a line to tell APRS to skip that map.  Also you can add some
comment lines at the designated space in the file (beginning with *)
so that you can leave notes as to what that particular MAPLIST file represents. 
There is also a comment field for each map.  If you have no comments, you MUST
place a comma at the end of the line.

MAP HIERARCHY:  It is important to place maps in decending order.  The last
map in the list that contains the given cursor position will be used.  If a
larger map covering the same area as a smaller map follows it later in the
list, then the larger map will always be found last and will be used, instead
of the desired smaller map.  You can see the this effect, by using the MAPS-
HIERARCHY command.  If maps overlap in your area, use the MAP-ALT
command to temporarily see the map beneath the present map.  You can also use
the MAPS-OVERLAY command to overlay the larger map onto the present map.  Using
this feature, you could make two maps of the same area and scale.  On one you
could put rivers and roads, on the other you could put counties, property
lines, and grids.  Then by listing the gridded map first in the MAPLIST.apr
file, it would always be superceeded by the road map, but could be summoned
up by hitting the MAPS-OVERLAY command!

MAP FEATURES:  APRS displays all map features by drawing lines from point-to-
point.  Each feature begins with 0,0 followed by the line color and a name for
the feature, followed by pairs of x,y points using the scale you chose.  The
feature name is not used, but is useful for identification during editing.  In
APRS, there is no limit on the number of features, But the total number of
points must remain below 1500.  Since the MAPFIX.BAS program does, however,
display these feature names during on-line editing, there is a limit of
99 in the array used to hold these names temporarily.  The POINT values
are positive to the right and down.  The end of a feature is simply the 0,0
which starts a new one.  After the last feature, there is a special 0,-1 which
indicates the end of all feature information and the beginning of the labels
list.

MAP COLORS:  APRS recognizes certain map colors for turning on and off certain
map features.  For this reason it is a good idea to use my standard colors.  I
made most map features using the brighter colors since they are easier to see
on a color monitor outdoors.  In recent versions, you can change the background
color with the Tint command or dim all colors using the MAPS-FEATURES-DIM
command.  Map colors are automatically dimmed when you ask for a MAPS-BORDERS
display so that the map edges show up brightly.  Here are my standards.  The
* indicates that the color is uniquely recognized by APRS for special
handling such as the FEATURES command:

 0 - Black (normal background)     * 8 - dark gray (Railroads)
 1 - dim blue                        9 - Bright Blue
 2 - dim green                     *10 - Bright Green (Interstates)
*3 - dim cyan (Rivers)             *11 - Bright Cyan  (Major rivers, Coasts)
 4 - deep red (state roads)        *12 - Bright Red   (major roads)
 5 - dim violet                     13 - Bright Violet(special routes/events)
*6 - dim orange (state/county lines 14 - Bright Yellow (Cities,airports)
*7 - gray     (back roads)          15 - Bright White  (Labels and CALLS)

MAP LABELS:   Labels are drawn on maps at given lat/long coordinates.  The
labels are listed at the end of each map (up to 99).  Each label has a range
scale associated with it, so that not all labels are visible at all  range
scales.  As you zoom in to finer and finer detail, you can make more  labels
appear.  The first line in the labels list has a leading 0 and then any
any comments.   From then on to the end of the file, each line  consists of
4 fields separated by commas.  First is the label text (up to 12  characters
long) followed by the LAT, LONG and RANGE.  LAT and LONG must be  given in
decimal degrees.  The MAPFIX.bas program displays the location of the cursor
in decimal degrees for this purpose.  Labels are plotted right justified.  This
means they will be plotted to the left of the given point.  A way to visualize
how a label will appear is to assume the label has a following  period (.) and
that the period is the location where the label will be plotted.  Labels are
right justified so that they do not overprint station callsigns which are all
left justified.   Since absolute LAT/LONG reference is used, labels can be
transferred with out any change to any scale map.  You may decide to change the
range size so that the label shows up sooner or later on different maps.
Please note, however, that labels are printed on the normal EGA screen 24 line
raster, so they can be off their exact location by almost a full text line
vertically, and one full character horizontally.  Take this into account
when placing labels.

     You can also build APRS symbols directly into MAPS!  Instead of a text
label, simply make the first three characters of the label be a $ followed
by the symbol character, followed by a hexidecimal number from 1 to F that
indicates the desired color for the symbol.  The remaining 8 characters can be
used for a conventional label at the same location.  For example, look at the
VORTAC's (aircraft nav aids) that I added to the ALASKA maps.  They are listed
in the map file as $VEANC,lat,long,rng.  The V is the VORTAC symbol, the E is
hexidecimal for 14 or the color yellow, and ANC is the label for the ANChorage
VORTAC as it will appear on the map.

                       
EXAMPLE:  The following map file constitutes a trivial state map of Colorado.
The first 8 lines are the fixed format lines which define the origin and scale.
Next are the features for the state borders and for Denver.  Finally are
the map labels.  To see how this map looks, move the cursor to the center of
Colorado on the US map and page-down to the 256 mile scale.

  41.0, latitude origin   (equates to 0,0 in)  [Notice how comments can be on]
  110.0, long of origin   (coordinate system)  [the ends of these first lines]
  60, pixels per deg of lat/long               [and 1st line of each new line]
  39,LAT of map center    (For ur reference only. Value in MAPLIST.apr is what)
  105.5,LON of map center (is actually used as the center and Range for maps  )
  200,MapRange
  4,minimum range         (APRS does not use this, it now computes min range)
  * This single comment line can contain anything... more or less
  0,0
  6,Colorado state line
  59,0
  59,240
  479,240
  479,0
  59,0
  0,0
  14,Denver city limits
  300,68
  289,77
  300,85
  311,77
  300,68
  0,-1                            (0,-1 indicates end of map features)
  0,Comments or notes... etc      (   note that the 0, is required   )
  Colorado,40,105,200
  Denver,39,104,100

NOTE:  The 7th line showing a min range used to be important.  Starting with
a full scale map, each time you page-down (zoom in) you are doubling the value
of each pixel lat/long value.  If any of these numbers ever exceed the maximum
permissible value of 2 byte integer math (32,000) then the program will crash.
To prevent this, APRS assumes that there will not be any data points larger
than about 1100 and will not draw your map to a scale that would multiply this
number too big.  This is why APRS will not draw the USA map smaller than about
32 miles. 

MAPFIX.BAS:  This QBasic program may be used to make, test and edit your maps.
It helps you to quickly display single maps and to use the cursor to identify
individual map point coordinates.  It also has a readout of the cursor in
decimal degrees which is required for locating labels and map Centers.  It
can be used to add, move and delete map points and save a new file.  It can
overlay a GPS track history file over the map you are drawing so you can
make your roads as accurate as GPS!  It has a DIGITIZER INTERFACE SO YOU CAN
DIRECTLY DIGITIZE ANY MAP!  It can also GENERATE A 64 MILE APRS MAP DIRECTLY
FROM THE USGS 2,000,000:1 CD ROM.  BUT IT STILL TAKES 4+ hours to manually
reduce the number of redundant points from the CD from over 5 MBytes down to
a 15K APRS size!


MAPCNVRT.BAS:  This QBasic progarm may be used to convert any one map to a
different LAT/LONG origin or different Pixels-per-degree resolution.  Use it
with the QBasic editor for piecing together features from one map to cut and
paste into another map.  Say you are building a fine detail map, but
want to use the statelines and interstates from a larger map.  Just use the
editor to remove all unnecessary points from the big map, keeping all the
features that you want to retain and move to your new map.  Then save it with
a TEMPORARY name and then run it through MAPCNVRT.BAS to re-compute all of the
map points.  Then use this new file as the beginning of your new map.  You can
also use the point-add-delete function in MAPFIX.bas to fine tune these points.

TECHNIQUE:  See the sketch above (not available in text file) which shows
how simple it is.  Most maps have LAT/LONG lines around the borders.  If you
are using 240 pixels per degree for a state size map, then each LAT/LONG line
corresponds to a multiple of 240.  Simply mark on the borders of your original
map these values 240, 480, 720, etc.  Then make a smaller template which
matches the size of one square of LAT/LONG lines.  Draw a finer grid of lines
every 10 pixels on the template.  Then to locate the coordinates of any point
on the map, simply orient the template with a major LAT/LONG square, and
interpolate the point within the grid on the template which represents a 10x10
pixel area.    For transfering features from one map scale or
origin to another, Use the QBasic program called MAPCNVRT.BAS which will
re-compute all point values.  Then use a text editor to re-do the LAT/LONG
and range and to cut and paste the necessary map labels on the end.

CAUTION: since many highway maps are Lambert Conformal instead of Mercator
projections, use the center square in your map for making the template to
minimize errors.  Further, be careful of highway maps that only have tick marks
along the borders for LAT/LONG. If the map is not a Mercator projection, then
you cannot just draw a straight line from left to right connecting latitude
marks.  Longitude lines are straight on a Lambert Conformal, but not latitude
lines!

SPECIAL EVENTS:  Conversly, absolute accurracy is only important if there will
ever be a GPS or LORAN station involved in your net.  A map with little
relationship to true LAT/LONG is perfectly useable in some APRS applications
as long as all stations in the net are using the same map and no one is using
GPS.  So feel free to draw quick simple maps for special events even as small
as a few square blocks without worrying about exact LAT/LONG.  Objects on one
station screen will still be in the same location on all other screens!  Use
the Chess board example at 25N 90W to play chess on the air!  But GPS is
comming, be prepared!  (PACCOM TNC's now come with a GPS interface built-in!)

                          MORE ABOUT MAPS PART 2

     With the advent of low cost GPS, most mapmakers are now beginning to
add LAT/LONG to most new maps.  Our 7-11 convenience store maps now even
include map booklets which have a LAT/LONG grid on every page!  The grid lines
are 5 minutes apart which is exactly 10 pixels if you use 120 pixels per
degree as I did for some larger APRS state maps.  This means that each
grid square is a 10x10 pixel area from which map coordinates can be typed
directly into a text editor without any drafting aids!  Simply compute the
grid coordinates of the corner of each page in the book based on your overall
map origin and start entering points!

NOTES ABOUT STARTER MAPS:  Some of the larger starter maps that I provided use
a scale of 120 pixels per degree and have an origin that is suitable for about
a 400 mile square area.  This area usually covers from one to several states
and is good for area maps.  With the whole map visible, one pixel represents
abt .25 mile resolution.  The first step in customizing maps to your area is
to take the starter map and start adding roads and features in your area. 
Since all maps in the APRS system are limited to a maximum of 1000 data
points, however, these large area starter maps can usually contain only the
interstate roads, the state lines, and major rivers and 4-lane highways.  This
is perfect for most VHF applications.  But as more and more people add detail
closer to home, smaller maps need to be "spawned" off to make room for more
detail.  The following sections describe how to spawn maps and convert points
from one map to another.

MAP CENTERING:  Most of you do not live in the middle of a starter map and so
your detail will be off center.  To make a more pleasant transition as you
zoom into your area using APRS, you may want to simply change the center and
range of the starter map to be centered on your area with a range suitable to
the amount of detail you have added.  To do this, simply edit the line for your
starter map in the MAPLIST.apr file to your desired center and range.  Keep
the original starter map for others to use by adding a (*) to cause APRS to
skip it when loading the MAPLIST.apr file.  As the number of points in your
map grows, you may need to throw out some of the points which are beyond your
area of interest.  Use MAPFIX.bas to delete points.  See the next section on
map spawning.

O |                      O |                        O |
----------------------   ------------------------   --------------------
  |          |       |     |         ---------- |     |                |
  |  MAP A   |   *   |     |         | MAP C  | |     |                |
  |          |       |     | -----------      | |     |                |
  |          --------|     | | MAP B | |      | |     |                |
  |        *         |     | |       |*|      | |     |        *       |
  |                  |     | |       --|------- |     |         X|     |
  |                  |     | |         |        |     |         ----------
  |                  |     | -----------        |     |          |     | |
  |                  |     |                    |     |          |     | |
  --------------------     ----------------------     -----------|------ |
                                                                 | MAP D |
   NEW CENTER & RANGE           MAP SPAWNING             MAP     ---------
                                                      CONVERSION

MAP SPAWNING:  In the figure above, map A is the original starter map with the
origin at O.  Using 120 pixels-per-degree resolution, all points within a
square area 8 degrees on a side (about 400 miles) can be resolved with pairs
of 3 digit numbers.  As the number of points in such a regional area map fills
up towards the 1500 limit, it is necessary to start new smaller area maps such
as B, C, and D above to permit finer detail to be added.  Spawning a new map
is easy.  Simply use a text editor to create a new mapfile and copy all of the
features out of the original map that fit within the new map area. Then save
this new map and add its name to the MAPLIST.apr file giving a center and range
appropriate to the new smaller area covered.  Now add new roads and features in
the area of interest.  Notice that since the same origin and 120 pixel-per-
degree scale are still used among all maps spawned from the same starter map,
features and points can be moved among those maps by simply cut-and-paste.

MAP CONVERSION:  When it is desired to move features and points from one map to
another map which has a different origin (X) or resolution, then use the
MAPCNVRT.BAS program.  First spawn a new map which contains all of the points
that are to be moved.  Then run the MAPCNVRT program giving the new origin and
resolution.  The resulting MAPTEMP.MAP file contains a copy of those features
and points ready to be cut-and-pasted into the new map (D) with the new origin
(X) and resolution.  This process is useful when creating finer detail maps of
an existing area and you want to transfer the interstates and larger map
features down to the finer detail map without having to re-do the data points.
You can use MAPFIX.bas to add new points to a road when building a finer detail
map, or to delete points when building a larger map where extra fine detail
points are not needed.

PIXELS-PER-DEGREE:  Although my early regional maps used 120 pixels per degree,
most of the newer maps generated from my CD rom use at least 450 to 600 pixels-
per degree.  This gives finer detail resolution on the smaller 64 mile maps. 
You can use 1200 ppd to resolve down to large city blocks, but to get them
accurately, you should consider 2400 ppd which can resolve down to about 100
feet.  Notice that as you increase the number of pixels-per-degree, you also
reduce the maximum size that a map can cover.  This keeps the numbers from
getting too large and causing an overflow condition.  A 1200 ppd map should
be used for map areas less than 50 miles and so forth.


AUTOCAD MAPS!   Jim Krist KG8GE has done a marvelous job of writing programs
to use AUTOCAD to make APRS maps.  He has done every street in the town of
MARION Ohio.  HIs program is named PLT2MAP and permits you to use a CAD plotter
to make AUTOCAD maps and then convert them to APRS.  Registered copies of his
software can be obtained for $25 from him at 315 Hane Ave, Marion, Ohi0, 43302.
I am not familiar with AUTOCAD, so if AUTOCAD is your bag, you might be
interested in his software.  Remember, however, that if you have a digitizer
tablet, you can draw APRS maps directly with the APRS MAPFIX.bas program.

