Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
On Thu, Feb 06, 2003 at 10:22:18PM -0600, Curtis L. Olson wrote: So, could the Lambert Conformal Conic be the projection I am looking for ? Any help or pointers are appreciated. You might be thinking too hard about this. Yeah, I guess. But then, I'm too often a perfectionist ;-) $x = $w/2 + ($lon - $center_lon) * $deg_to_nm * $scale * $xfact; $y = $h/2 - ($lat - $center_lat) * $deg_to_nm * $scale; ($x, $y) is the coordinates (in screen space) where you should draw the object. This is known to work pretty well over a local area (assuming my typing is correct, I didn't overlook something, and you can get past the pseudo-perl syntax.) :-) Thanks, this will at least for the testing phase a good start. I have been thinking about something like this, but the ironing out the formulas above ... I just didon't how to put it all together. perl's no problem. I've did quite a bit of perl hacking some time ago. Thanks again, Manuel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Manuel Bessler writes: $x = $w/2 + ($lon - $center_lon) * $deg_to_nm * $scale * $xfact; $y = $h/2 - ($lat - $center_lat) * $deg_to_nm * $scale; ($x, $y) is the coordinates (in screen space) where you should draw the object. This is known to work pretty well over a local area (assuming my typing is correct, I didn't overlook something, and you can get past the pseudo-perl syntax.) :-) Thanks, this will at least for the testing phase a good start. I have been thinking about something like this, but the ironing out the formulas above ... I just didon't how to put it all together. perl's no problem. I've did quite a bit of perl hacking some time ago. I worked this stuff out as part of perl-tk moving map / approach deviation grapher I'm building for a side project. I hope to get authorized to release as open-source some day... been working a couple angles, we'll see... Regards, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Norman Vine writes: This works fine for a 'map' but straight lines will not be great circles which AFAIK is still the standard for *most* aviation 'charts', both paper and electronic versions It depends on scale. World Aeronautical Charts (1:1,000,000) and VNCs/Sectionals (1:500,000) use Lambert Conformal Conic projection, so that (as Norm suggests) a straight line drawn on the chart will really be a great circle. VFR terminal area charts (1:250,000) use Transverse Mercator projection since they cover a smaller area. All the best, David -- David Megginson, [EMAIL PROTECTED], http://www.megginson.com/ ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
I couldn't find any good info on what kind of map projection technique to use for the ND. ie. mapping lat/lon to x/y-screen coord. I took a look at the OpenGC source, and as far as I understand, it uses a technique which converts RijksDriehoeks to Hayford. I tried to google a bit on this, but couldn't find much. Basically, RijksDriehoeks seems to be a technique developed specifically for the Netherlands... Did a little more research... (blindly shooting some search requests at google) Something that came up was, the Lambert Conformal Conic Projection. I also had the chance to ask a real airliner pilot. He said that on A340 and B744, a line on the NDs represents the shortest path between two points, ie. a Great Circle route. He also said that on older NDs (A300 or A310, I forgot which he mentioned) the line is not a Great Circle Route. So, could the Lambert Conformal Conic be the projection I am looking for ? Any help or pointers are appreciated. Regards, Manuel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Manuel Bessler I also had the chance to ask a real airliner pilot. He said that on A340 and B744, a line on the NDs represents the shortest path between two points, ie. a Great Circle route. He also said that on older NDs (A300 or A310, I forgot which he mentioned) the line is not a Great Circle Route. So, could the Lambert Conformal Conic be the projection I am looking for ? Any help or pointers are appreciated. google(map projections great circle straight line) Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Manuel Bessler writes: Did a little more research... (blindly shooting some search requests at google) Something that came up was, the Lambert Conformal Conic Projection. I also had the chance to ask a real airliner pilot. He said that on A340 and B744, a line on the NDs represents the shortest path between two points, ie. a Great Circle route. He also said that on older NDs (A300 or A310, I forgot which he mentioned) the line is not a Great Circle Route. So, could the Lambert Conformal Conic be the projection I am looking for ? Any help or pointers are appreciated. You might be thinking too hard about this. The following seems to work really slick for me (assuming you are doing smaller area maps or don't care about some distortion as you get towards the top/bottom of the map. Even if this isn't quite good enough for your needs, it will get you out of the gate running and you can come back later and do something fancier. Pick some ($center_lon, $center_lat) to be the center of your map. Then calculate $xfacter = cos( $center_lat * $deg_to_rad ) Now set $h = height in pixels of your display and $w = width in pixels of your display. You also want a $scale variable that is set to the something like number of pixels per nautical mile. Also note that to convert from a degree of latitude to nm, multiply by 60 (i.e. there are 60 nm for every degree of latitude.) Ok, so you have all that? Now if you want to draw something on your map (i.e. a VOR) at some ($lon, $lat) just use the following formula: $x = $w/2 + ($lon - $center_lon) * $deg_to_nm * $scale * $xfact; $y = $h/2 - ($lat - $center_lat) * $deg_to_nm * $scale; ($x, $y) is the coordinates (in screen space) where you should draw the object. This is known to work pretty well over a local area (assuming my typing is correct, I didn't overlook something, and you can get past the pseudo-perl syntax.) :-) Regards, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Curtis L. Olson writes: You might be thinking too hard about this. The following seems to work really slick for me (assuming you are doing smaller area maps or don't care about some distortion as you get towards the top/bottom of the map. Even if this isn't quite good enough for your needs, it will get you out of the gate running and you can come back later and do something fancier. Pick some ($center_lon, $center_lat) to be the center of your map. Then calculate $xfacter = cos( $center_lat * $deg_to_rad ) Now set $h = height in pixels of your display and $w = width in pixels of your display. You also want a $scale variable that is set to the something like number of pixels per nautical mile. Also note that to convert from a degree of latitude to nm, multiply by 60 (i.e. there are 60 nm for every degree of latitude.) Ok, so you have all that? Now if you want to draw something on your map (i.e. a VOR) at some ($lon, $lat) just use the following formula: $x = $w/2 + ($lon - $center_lon) * $deg_to_nm * $scale * $xfact; $y = $h/2 - ($lat - $center_lat) * $deg_to_nm * $scale; ($x, $y) is the coordinates (in screen space) where you should draw the object. This is known to work pretty well over a local area (assuming my typing is correct, I didn't overlook something, and you can get past the pseudo-perl syntax.) :-) This works fine for a 'map' but straight lines will not be great circles which AFAIK is still the standard for *most* aviation 'charts', both paper and electronic versions Cheers Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Norman Vine writes: This works fine for a 'map' but straight lines will not be great circles which AFAIK is still the standard for *most* aviation 'charts', both paper and electronic versions Fair enough ... I guess it all depends on the needs of the end application. It's about as simple as you can get though and it will get you out of the gate so you can work on making pretty pictures. Once you have something working you could come back and do a fancier projection. Regards, Curt. -- Curtis Olson IVLab / HumanFIRST Program FlightGear Project Twin Cities[EMAIL PROTECTED] [EMAIL PROTECTED] Minnesota http://www.menet.umn.edu/~curt http://www.flightgear.org ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Hi Norman, I heard about this... this still doesn't help me with the specific projection technique used on NDs. the proj package can do the conversion for you I understand that, but my what I would like to know is: Is the RijksDriehoeks conversion to Hayford as used by OpenGC the method used in the real NDs by Honeywell(or whoever makes those in Boeings/Airbuses) ? Is there any info about this on the web ? References ? I am wondering about the RijksDriehoeks thing because it seems to be a method specifically designed for the use in Netherlands. [Do I make it harder than it actually is ? Am I missing something ?] Finding an algorithm is not the problem, but knowing which algorithm to use is. Any way here is a hint trf_nonpolynomial.csv: 19914,RD NewNetherlands - onshore.,9809,52.0922178,5.23155,,,0.079,155000.0,463000.0,9001,9110,8901,1995-12-02 00:00:00,Nederlandse Commissie voor Geodesie publication 30.,EPSG,,95.30 96.29 ??? I guess I don't understand... not enough hint for me :) Bye, Manuel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
[Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Hi I am working on something similar to OpenGC, but not OpenGL based, but rather xlib-based... (its supposed to run on lowlevel Pentiums w/ non-3D accel graphics cards, maybe even 486s) I couldn't find any good info on what kind of map projection technique to use for the ND. ie. mapping lat/lon to x/y-screen coord. I took a look at the OpenGC source, and as far as I understand, it uses a technique which converts RijksDriehoeks to Hayford. I tried to google a bit on this, but couldn't find much. Basically, RijksDriehoeks seems to be a technique developed specifically for the Netherlands... Does anyone have some tips for me? What do Honeywell/Boeing/Airbus type NDs use? Do I make it harder than it actually is ? Thanks, Manuel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Manuel Bessler writes: I am working on something similar to OpenGC, but not OpenGL based, but rather xlib-based... (its supposed to run on lowlevel Pentiums w/ non-3D accel graphics cards, maybe even 486s) I couldn't find any good info on what kind of map projection technique to use for the ND. ie. mapping lat/lon to x/y-screen coord. I took a look at the OpenGC source, and as far as I understand, it uses a technique which converts RijksDriehoeks to Hayford. And how is this going to tie into FlightGear ??? http://www.remotesensing.org/proj/ Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
On Sat, Feb 01, 2003 at 06:04:21PM -0500, Norman Vine wrote: Manuel Bessler writes: I am working on something similar to OpenGC, but not OpenGL based, but rather xlib-based... (its supposed to run on lowlevel Pentiums w/ non-3D accel graphics cards, maybe even 486s) I couldn't find any good info on what kind of map projection technique to use for the ND. ie. mapping lat/lon to x/y-screen coord. I took a look at the OpenGC source, and as far as I understand, it uses a technique which converts RijksDriehoeks to Hayford. And how is this going to tie into FlightGear ??? I am not sure whether I'll use one of the existing interfaces (eg. the one for opengc,... probably I'll start testing w/ the telnet interface.) or I if write one (yeah, another one :-) right now, its not connected to anything yet, just keyboard input and joystick for easy test input. http://www.remotesensing.org/proj/ I heard about this... this still doesn't help me with the specific projection technique used on NDs. Also, I have only started digging into all this GIS and similar stuff (also for possible use for my day job) There's a lot of stuff to learn :( Thx, Manuel ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
Re: [Flightgear-devel] [more or less OT] Map Projection on Navigation Displays
Manuel Bessler writes: On Sat, Feb 01, 2003 at 06:04:21PM -0500, Norman Vine wrote: Manuel Bessler writes: I couldn't find any good info on what kind of map projection technique to use for the ND. ie. mapping lat/lon to x/y-screen coord. I took a look at the OpenGC source, and as far as I understand, it uses a technique which converts RijksDriehoeks to Hayford. http://www.remotesensing.org/proj/ I heard about this... this still doesn't help me with the specific projection technique used on NDs. the proj package can do the conversion for you Also, I have only started digging into all this GIS and similar stuff (also for possible use for my day job) Now why did I suspect that :-) Any way here is a hint trf_nonpolynomial.csv: 19914,RD NewNetherlands - onshore.,9809,52.0922178,5.23155,,,0.079,155000.0,463000.0,9001,9110,8901,1995-12-02 00:00:00,Nederlandse Commissie voor Geodesie publication 30.,EPSG,,95.30 96.29 Norman ___ Flightgear-devel mailing list [EMAIL PROTECTED] http://mail.flightgear.org/mailman/listinfo/flightgear-devel
