AviaDBM - FAQ
1. Can I create an ISAM database with one GEN
program
and then create a new image with another GEN program ?
Yes. This is the method to use when creating an update for a discontinued model.
Sometimes you will end up with a new image which is too big for your unit, so you must be prepared to impose some geographical limits.
2. What is the best method of removing excess data from the ISAM db ?
You can now make a whole-world ISAM db and select your own area for a new image.
If you really wish to remove data from the ISAM database, make a *bat.all file (or files) containing the countries you wish to remove. This is done by listing the APT section and selecting File/SaveAs Batch Dump. Then edit the ADD| commands to read DEL| and re-input as a Batch Update. Don't forget that you can make large space savings by re-compiling the SUA section and applying compile filters, and you can remove complete sections by deleting their ISAM files.
3. How long does my licence last
?
It is everlasting. You may request new licence codes for new systems, and download future versions of the package at no extra cost.
4. When using Create ISAM with my Pacific database I get an error message during the SUA section.
This is due a manufacturer's compile error, the first area in section (b) is corrupt (see "Imperfections" document). This area has no names, and AviaDBM does not attempt to change this situation. You can of course dump the SUA to a *sua.all file, edit out the bad area, and re-compile it.
5. Isn't there an easier method of specifying SUAs ?
Not really. The method closely follows the publication method used by most aviation authorities, and program ConvAIR is provided to translate published airways data into this format.
6. Why do I get "No Loader Available" when I try to update my 196 or 295 ?
These units require a loader program to be sent to the GPS before the database image can be accepted. These loader programs are held in the original .awp or .rg1 file, and this file needs to be located in the same directory as your new image.
7. I have bought an update over the Internet, but how do I get the Image file ?
The update comes in a .exe file which can be 'unzipped' by WinZip. Open the .exe with WinZip and extract the .awp file. List any section of the .awp file using the appropriate GEN program, and a .img file will be created.
8. How do I know how much data will fit inside my GPS ?
There is no way to predict the size of any CreateImage operation other than by trying it. The GEN program will tell you if the image is too big, and by how many bytes. Try choosing narrower geographical limits, and measure the effect. The log also gives the image size in hexadecimal. Most units have 2Mb memory (200,000 in hex), but the 3Pilot only has 170000, the G90 and G95XL have 100000, the G95AVD only C0000, and the G92 has 180000.
9. I want to generate my own batch files, what is the format of the runway picture bytes ?
I am sorry to say that the decode of the picture bytes is rather complex. The thresholds are held as offsets from the airport co-ords, and are packed together with the runway heading and stripe orientation in such a way that they do not fit into byte boundaries. If you still want to try, ask me for the relevant section of my notes.
10. My new image has all dates set to the day it was created, can I change this ?
This feature was intended to provide final proof that the image was not created by the manufacturer, so that he could not be blamed if you made some mistakes. I can explain the location of these dates in the image, but they are little-endian hex values and you have to change the sumcheck bytes as well.
11. Can I migrate user waypoints and routes from one model of GPS to another ?
Yes, but there are restrictions due to the different record formats employed. You cannot simply use GPS_COM to download from one and upload to another. The procedure requires that you Import the .gar files into GPS_DBM and re-Export them in the new format.
12. My GPS is capable of 115,200 baud, but I get hang-ups and transmission errors at this upload speed.
I do too. I find things are better the newer the hardware and the shorter the interface cable. My 4 year old cheap laptop has no problems at 115k.
13. My GEN program has been OK for months, but now it keeps crashing.
If there has been an unexpected interruption on the system it is possible that an ISAM database index has become corrupted. Try deleting all the files in subdirectory 'db45', or at least all the *.dtx files, and start over.
14. I have made a new image file which is over two times the maximum size, and find that many of the records are corrupt when viewed with my GEN program.
Many of the data structures hold addresses of items within the image and have become too large. Since the primary limit is image size, GEN does not check for this occurrence in an image which will be too big, preferring to create it anyway as an indication of the resulting size.
15. Can the limit of 256 countries be increased ?
No, sorry, it is built into the database structure, since every record holds the country number in one byte, giving it a range of 0 to 255. Current images have 254 countries, so there are only two spare slots. You can remove unused countries by checking View/OptimiseCountries when making a new image, but this will invalidate any routes inside your unit because AVD waypoints will be held using the previous country numbers. The solution is to read the routes out into a routes.gar file, and upload them again after changing the database, because the countries are held as two letter idents outside the unit.
16. I made a G90 image from data obtained from a G3P image, and the airports have fewer frequencies listed.
The modern units can accommodate 16 different types of airport frequency (a 4 bit value), whereas the older units can only represent four types (a 2 bit value). G90_GEN maps the new values onto the old ones, and combines obvious ones such as Taxy and Ground, but has to omit the rest. If this mapping would result in two identical entries, only one is included.
17. Is it possible to edit the Approaches section of the database ?
Although the Approaches data is held in the ISAM database, GPS_DBM does not have facilities for displaying or manipulating it. You can however create a text dump using GPS_GEN SaveAs [*.apr.all], make changes to that with an editor, and re-compile it. The compiler replaces all the data for a given airport each time any approaches for that airport are found in the input file.
18. Why is there a limit to the number of lines in a listing to screen ?
This seems to be an operating system problem. Windows 98 cannot handle a scrolling window deeper than 32767 pixels, about 2040 lines in the default font. Windows XP has no obvious limit, but has a bug which causes the scroll bar to fly back to zero if it is touched with the window scrolled beyond 32767 pixels. On balance I thought it better to place a limit of 2000 lines in the software.
19. I made a new image but the SUAs do not display properly, if at all.
This can happen if you make the E/W
dimension of your geographical selection too large, and is
due to a limitation of the software in the gps unit.
My G3Pilot has problems if Europe and
20. The latest G92 and G3P database cycles generate hundreds of errors when making an ISAM database.
This problem is described in Documentation>COMPILATION ERRORS IN GARMIN DATABASES para 4b (second half). The work-around is to use an update for a current unit and impose geographical limits to keep the image size below the limit for your unit. In other words, treat your unit as obsolete, which it will be soon no doubt.
21. What is the format to be used
when specifying geographical co-ordinates.
There are two different formats in use for expressing lat/longs, being Ndd°mm.mmm Eddd°mm.mmm for the main waypoint types and approaches, and Nddmmss Edddmmss for the SUA, FSS, and TCC sections. In GEN programs, all input functions (including dialog boxes) will accept these alternatives, but DBM only accepts the dd°mm.mmm versions.