MGL Avionics MapMaker 2

MGL Avionics
MapMaker 2
User guide
General
The MGL Avionics MapMaker application is used to convert digital map images into the
raster map format suitable for MGL EFIS systems.
Note: MapMaker2 produces EFIS raster maps compatible only for EFIS systems
supporting this format. The Mapmaker2 format replaces the format used by the original
MapMaker application. The formats are not compatible with each other.
The MapMaker2 format can be used with MGL Odyssey/Voyager G2 as well as iEFIS G2
and G3 systems that have firmware upgrades suitable for this format.
The MapMaker2 application
The MapMaker2 application is used to geographically reference map images, process the
maps into “tiles” and finally collect tiles into “map files” suitable for use with the EFIS.
MapMaker2 is a Windows executable that can be used on both 32 and 64 bit systems
(Windows XP onwards). 64 bit systems with memory greater than 4 Gbytes may be
needed to load and process very large images (high number of horizontal and vertical
pixels).
Source maps
Source maps would be digital aviation maps (any maps could be used but aviation related
maps would be the normal choice).
Source maps must be in TIFF or JPG format. Other formats are not currently supported. If
needed use one of the many available converters or editors to convert to TIFF format
(recommended as it is a lossless compression format). A good example of a free
application that can be used is: IRFANVIEW.
Geographic Referencing
Before a source map can be used it needs to be referenced. Two geographic coordinates
need to be identified from the image, one near the top left corner and another near the
bottom right corner.
Two methods are provided to fine tune the referencing done after the two corners have
been defined:
Lambert Conical projections
If the map source is an accurate Lambert Conical projection either for the Southern or
Northern hemisphere the meridian lines can be slewed to match the map image. This also
defines the radius of the latitude lines towards the poles and hence the bow of the latitude
lines on the map.
Once the upper left and lower right coordinates have been defined, slew the meridians
using the bottom left and top right meridian slew function.
Undefined projections
All other projections including Lambert Conical that are not accurate can be used as well.
In this case each degree intersection on the map is individually moved to the correct
location. This allows referencing effectively on a per degree bases regardless of map
projection.
Select the desired geographic referencing method using the Map Processing Options
dialog.
You can switch between the two referencing methods at any time to find the best one to
suit the map.
Georeferencing using tfw files.
Some TIFF files can be used with matching .tfw files which contain geographic referencing
information. However this cannot be used as there is no projection information at all and
also no information on the extent of image you need to convert.
The information is only useful for a very approximate position and accurate for a single
pixel (usually center pixel but it could be any pixel).
TIFF files with geotags.
Some TIFF files are created with referencing information that is much better than the tfw
file format offers. At current this is not used but it may be in a future edition of MapMaker if
this proves useful and accurate enough.
Symbols
Reference symbols (pointed to by yellow arrows) come in different colours:
Blue: This is the geographic referencing location. There must be two of these defined: One
near the left top and one near the bottom right of the map. The location does not have to
be on a full degree intersection. If it is not, the full degree tile to the left,top or bottom,right
will be included during tile generation.
Note: If the position is not on a full degree intersection the actual map position of the blue
symbol needs to be moved slightly to move the green reference symbols to fall exactly on
full degree boundaries. You can see an example in the above image: The blue symbol has
been moved slightly higher and to the right which also moves the green symbols so that
they fall exactly on full degree intersection.
Green or red: These are the degree intersection markers. Each marker has an identifier
which is the degree offset from the top left marker which is 0/0. This is relevant if you use
universal geographic referencing as you can place each marker individually.
If a marker is red it means that its degree position does not correspond to its map position.
This can only happen if you placed the markers at invalid locations relative to each other.
Your geographic referencing is completed when all markers are green (except the two blue
ones) and correspond to full degree intersection locations on the image.
If you exit the program or load another map source your geographic referencing will be
saved in the same folder as the map source you loaded. The name for the file that
contains the information is the same as the map file name but with the file extension “.INI”.
When you load the same map file again your geographic referencing will be loaded as
well.
Your operating system may hide file names with this file extension. Set up your windows
folder options to show “hidden files” if you need to work with these files. You can edit these
files in a text editor such as Windows Notepad should you ever need to.
Finalizing geographic referencing
With Lambert Conical projections, in particular with the blue reference markers not on full
degree intersections you may need to work around the map two or three times to align the
green markers exactly. Use the top/left and bottom/right buttons and by clicking near the
existing blue markers you can move them slightly to align the markers.
After this verify the meridian slew and correct if needed. After correcting the meridian slew
you may again need to correct the top/left and bottom/right markers as they interact.
Repeat this until the referencing is perfect.
If you cannot get it right perfectly it may be that your map image is not accurate. This is
quite common with older image files that may have been scanned from paper maps.
In such a case simply select the universal geographic referencing from the map
processing options and move every degree intersection to its proper location. This is done
very easily: Simply click on the green/red symbol (The text “Moving n/n” appears in the text
box below the map) – then click on the location you want the reference marker to lie on.
Verify all markers to be properly located, then double check that your top/left and
bottom/right geographic position is in fact correct and matches that of the map (If this is not
correct the EFIS will be displaying the map in the wrong location).
Once you are satisfied you may process the map to create the map tiles.
Map Tiles
EFIS maps are based on tiles. A tile is defined as a rectangular image that is always 600
pixels high and 600 pixels wide at the equator – as you go north and south the width in
pixels decreases.
Tiles come in different map resolutions expressed in degrees: 0.25, 0.5, 1, 2, and 4
degrees.
The EFIS map file can contain up to 8 x 8 degrees worth of tiles in all 5 resolutions or a
subset of these. Typically you should create resolutions for 4,2,1 and 0.5 degrees. 0.25
degrees should only be used on small scale maps or perhaps on map inserts (smaller
sections of maps processed as separate maps).
0.25 degree tiles if used for all maps will significantly increase the size of these maps
without real benefit as the EFIS can construct 0.25 degree tiles from the 0.5 degree tiles
quite well. Maps in 1:500.000 or larger format do not contain enough small scale detail to
make 0.25 degrees worthwhile.
Processing the map
Load a map and verify that geographic referencing is good.
Select “Map processing options” from the menu.
Do not select 0.25 degrees unless you have a suitable source to make this worth while.
Adding this resolution will approximately double the size of your EFIS map files. The EFIS
can create this resolution from the 0.5 degree tiles by reusing each pixel 4 times – at the
cost of a slightly degradation of the displayed map image. It is recommended to
experiment before deciding to include the 0.25 degrees processing option.
You can select how many colours each tile may have. Mapmaker includes a very good
algorithm to select the best combination of colours to represent your map. Generally a
selection of 64 colours provides a good compromise between image quality and file size.
Note that this applies to each tile – each tile can have its own variation of colours.
Most maps render well without dithering. You can select from several dithering algorithms.
You will find detail descriptions on the strengths and weaknesses of each on the internet
using a search engine.
Dithering is a method to fool your eyes into seeing more colours than there actually are.
This can be used in combination with the above colour count setting. Feel free to
experiment and view the results using the built in map file viewer.
The “DX” buttons can be used to transfer the relevant settings to all maps in your project.
When done, select “Process source map (create tiles)” from the menu.
The process Viewer will pop up. The MapMaker application will now process every tile
(you will see the tiles flashing past as they are processed).
This involves transforming the source polygon (the source tile) from the source map which
is not rectangular to a rectangular representation of the correct pixel height and width. The
process involves “super sampling” and “sub sampling” techniques to avoid tearing the
image in particular at large resizing ratios. The result is a pleasing image that will look
good when rendered on the EFIS display.
Once the tile has been transformed and sampled it is converted to a standard image file in
GIF format (GIF87 is used). The tile is then written out to the “tiles” folder of the current
project. The file name is made up from two numbers – the first single digit is from 0 to 4
and specifies the tile resolution. The next number is the tile number. Number “0” starts at
W180N0 degrees and numbers increase to east until E180 is reached after which the tile
number increases by one to start again at W180 a bit more to the south.
You can view any of these tiles in a suitable image viewer or editor.
Creating EFIS map files
The final process once all tiles have been created is to create the EFIS map files.
This should be done only once you have processed all of your map sources and created
all of the tiles needed.
Select “Create EFIS maps from tiles”.
MapMaker collects all tiles from the “Tiles” folder of the current project and creates the
correct map files, inserting these tiles into the map files.
These are the final map files you will transfer to the EFIS.
EFIS Map files
EFIS map files cover a fixed area that is 8 x 8 degrees in size. The file name refers to the
geographic position of the top left corner of the 8 x 8 block.
Each EFIS contains all of the tiles belonging to this geographic block, all of the resolutions.
The geographic coverage of each map has been chosen to offer a good compromise
between size of the file and number of files needed to cover a typical area.
Testing your maps
Once you have created your maps it is a good idea to test them. You can use an EFIS of
course but it is much easier to use the built in map file viewer.
Select “View EFIS map files”
The viewer allows you to enter a geographic coordinate and select a desired tile
resolution. Click “View” when you have made your selection.
What you see here is exactly the way the EFIS will display the map.
Note: Crossing tile boundaries latitude wise (top to bottom) will introduce a slight horizontal
discontinuity that gets worse the further away you move from the viewing location (center
of the map). This is because tiles are rectangles so meridian lines are always vertical but
area decreases as you go towards the poles. The tiles will always match near or at the
viewing position which is what you are interested in with the EFIS. The rectangular tile size
suits the EFIS making it possible to always display a map properly “North is vertical”
regardless of how much area a collection of maps represents.
Tile based formats are used because they are very fast to load (you only load the tiles you
want to view – no need to load up to 4 maps which could be many hundreds of megabytes
in original size).
Projects
MapMaker supports the concept of “projects”. Before you can view and reference maps
you need to create at least one project.
Select “Create a new project or load an existing project”.
A project name must be a valid Windows folder name as the name is used to create a
project folder with that name.
A good name map be “USA”, “UK”, “Europe” - use the area you want to create maps for as
name. You can use any name of course, perhaps “USA West”.
Inside this folder there will be a few more created:
EFIS Maps – this will hold the created EFIS maps
Tiles – this will hold the tiles
Source Maps – this folder is for your convenience, we suggest you copy your source
maps into this folder for loading and processing. You can however locate the map sources
anywhere you like.
Temp – this folder is used during map creation to hold intermediate results
You can maintain as many projects as you need and switch between them at will.
Note: As you open maps for viewing or geographic referencing they are automatically
added to your project.
You can view the maps in your project by choosing the Batch → View Edit Project menu
function:
You can delete maps you do not want in your project. This is relevant for batch processing.
Processing a batch of maps
It is possible to use MapMaker to process all of the maps in your current project.
Select “Batch → Execute Batch”
After clicking the “Run Batch” Mapmaker will load each map and process it to create the
tiles for that map based on the maps options selected.
Please ensure that you have completed geographic referencing for all of the maps before
using this function.
After completion you can use the “Project → Create EFIS maps from tiles” to create the
map tiles.
Important:
It is recommended that you delete all tiles in your tile folder before running the batch or
starting a new map update (assuming you do not need any old tiles from a previous
session).
Problems
Memory:
The biggest single issue is memory. Some aviation map sources can be very large, for
example the current U.S. FAA maps need around 1 Gbytes of memory to fully load.
MapMaker must load the entire file into memory as image due to the super sampling
techniques used. This memory must be contiguous (one single linear block) and is also
used to display the map on the screen based on the zoom level (the entire map is
supersampled into the displayed image).
32 bit versions of Windows may not allow allocation of such a large block of memory as
the available memory tends to fragment. You may be able to use such versions if you run
mapmaker after boot without using any other applications and there is little loaded in the
way of hidden applications and drivers.
64 bit versions of Windows tend to be much better in this regard if you have 4 Gbytes or
even more RAM available.
Other possible solutions:
Cut the source image into two map files using an image editing program.
Crop the map image to remove the borders (Often large white borders with a lot of legends
and information that is not needed for our maps).
Reduce the image resolution. Use a good editor that can apply a good sampling technique
to reduce the effect this may have on the image quality.
Even a relatively small reduction in image size (horizontal and vertical size, not the file
size) can make a big difference as halving horizontal and vertical pixel count reduces the
size of memory needed to a quarter !
Map overlap:
Most maps are designed to overlap each other so the map edges tend to have partial
degrees which can be ignored – the full degree will appear on the adjoining map.
Make sure you do not create the same tile from two adjoining maps.
Tile numbers:
The Tiles folder may have to hold a very large number of tiles if you have many source
maps. This can slow down operations as Windows will spend a lot of time searching
through the folders to find new entries and locate tiles.
Clearing the tiles folder:
It is recommended to clear out the tiles folder before you start fresh to avoid creating maps
with tiles left over from previous work.
Maps with Inserts:
Some maps may have inserts, a good example is the Los Angeles map used in this
document.
It is recommended to use an image editing program to cutout this insert and save as a new
map. Include this in your project as 0.25 degrees per tile resolution.
It is highly recommended to remove this insert from the source map after that as it may
cause confusion if the EFIS shows the insert when you are flying over the ocean as it
would in this case. Simply edit it out (in this case use a blue colour to wipe out the insert).
1:250.000, 1:100.000 maps:
Some areas may be covered in high resolution small scale maps, usually close to major
centres. It is recommended to include those as 0.25 degree tiles.
1:1.000.000, IFR maps:
Consider using 4 and 2 degree tiles for large scale maps or IFR maps.
1:500.000 maps:
These maps work best for 0.5 and 1 degree per tile but can also be used for 2 and 4 if no
other, more suitable maps are available.
Map updates
Invariably, maps will get updated and changed. MapMaker can deal with this provided the
scale and position of the map in the image has not changed – this would require redoing
the referencing.
Most maps are now directly created from digital data without going through a paper and
scanning process. This means geographic referencing does not change.
If the filename has not changed then simply copy the new map file over the old one and
process it.
If filenames change from update to update consider renaming the file to your own
standard.