Compressed ARC Digitized Raster Graphics
Is the NGA standard for distributing scaned NGA charts.
The full standard is availble from the NGA website as MIL-C-89039 but basically a chart is scaned then down sampled to 150microns per sample, divided ito 1563x1563 frames, converted to 216 colors and compressed using Vector Quantization (VQ). The data is then wrapped in a NITF header.
The frame files follow a rigorous naming convention:
The extension of the file encodes the chart series in the first two characters and the zone of the file (each zone is a band of latitudes numbered 1-9 in the Northern hemisphere and A-J (skip "I") in the southern hemisphere) in the last character.
The File name contains a radix 34 offset into the zone, in the first 5 characters followed by two characters for the version number and one character for the producer code.
Question
We are interested in discussing the development of the following project with possible Falconview integration: A homeland security patrol tracking system that would track aircraft and discriminate when an aircraft is assigned a specific infrastructure sector and is in patrol mode. As the aircraft approaches the location of a particular infrastructure site (Patrol check location) within each sector, the mapping system will generate a patrol log automatically – as long as the crew confirms that it is conducting reconnaissance and not simply flying a direct path enroute to some other location. This would be similar to the system used by security guards who conduct roving patrols at an installation and check in at each spot on their rounds. I believe this could be done through making shape data files over each location of critical infrastructure and building the code required to generate a report when the icon of an aircraft goes over top of that shape data file. The flight tracking system known as Automatic Dependent Surveillance Broadcast (ADS-B) under development by the FAA could be one of the components. This ADS-B system, if combined with Falconview and ArcView, proves to bring about this patrol log capability. If anyone has interest or is working on similar projects, please contact us. Thank you.
-- Trp Nine - 20 Apr 2006
I am curious what your "correct edition number" list is. What you are doing sounds like the "Tools->Data Administration...-> Chart Currency...." functionality in FalconView.
I don;'t have the CADRG spec handy but the version of the CADRG file is encoded in the file names 6th and 7th characters. If you are looking for the edition of the paper chart that the CADRG frame came from, them that is much harder since there could be 4 paper charts meeting in the frame. The Chart edition is stored in a structure that can accomadate this but it is harder than reading the 12 bytes. (This is also not in the cov file).
We do not publish the COV format. It has been replaced by a SQL database in 4.0 where we are exposing a wide variety of functions via the MapDataServer so people can programmatically access it.
Finally you may want to look at the IMapDataManager interface which will return all the frames of a particular map that intersect a bounding rectangle.
(PS I am going to move this topic in a few days)
-- Main.ChrisBailey - 18 Apr 2006
Thanks Chris. Unfonrtunately the US won't supply foriegn nations with the Chart Supplement Disk. So the Tools -> Data Admin -> Chart Currency tells you all your charts are out of date. I've managed to pretty much successfully pluck out all the chart series and editions from every TPC file that is listed in the COV file. Simply opened a byte stream and hunted through the results a bit to pluck out the format.
I've read through the CADRG file spec, however I found it a little confusing in regards to reading in the Attributes section (It's been ten years since I did my Comp Sci degree :)
The source I used for the "correct edition number" was RAAF AIS ( http://www.raafais.gov.au/Pdf/cat_040903/cat_0409031.pdf) Product Catalogue, updated for the RAAF AIS CHAD (Chart Amendment Document = Aus version of US CHUM).
Does anyone publish any tools to edit ECHUM? (ECHUM is very limiting in Aussie obstructions) Regards, Scott
-- Scott Marshall - 19 Apr 2006
Sorry, the previous post is regarding CADRG files. I still require the standard filespec for ctpc.cov!
-- Scott Marshall - 16 Apr 2006
Found a work around. I've opened a FileInputStream, search the CADRG file for "TPC", then count 12 bytes along in the file and take the previous 5 bytes in as characters to get the Chart Series. To get the edition I've looked for an integer located between 17 and 28 bytes past "TPC". Anyone see a problem in this?
-- Scott Marshall - 16 Apr 2006
I was wondering where I could get the file specification for the map coverage files (e.g. ctpc.cov). I'm trying to program a third party tool to check all the chart series and edition numbers of all the TPC's against a plain text file (that has the correct edition numbers in it). I'd like to access ctpc.cov to get the path to each CADRG tpc file in order to look up the Chart Series / Edition number in each TPC CADRG file.
-- Scott Marshall - 15 Apr 2006
-- Chris Bailey - 21 Jun 2006
