geospatial - Calculating scale of an image -

-

i'm working on processing geo-spatial raster data, jog-a raster exact , know imagery supposed to scale of 1:250000, calculate in code not coming correct values thought ask help.

here bounds of single image , other values needed calculations. (coordinates in degrees, epsg:4326)

  • meters per degree: 111319.49079327358
  • image size: x: 1536 y: 1536

  • dpi: 90

  • upper left: longitude: -89.54314720812182 latitude: 33.6529242569511

  • upper right: longitude: -88.8578680230458 latitude: 33.6529242569511
  • bottom right: longitude: -88.8578680230458 latitude: 33.13518696069031
  • bottom left: longitude: -89.54314720812182 latitude: 33.13518696069031

i thought say: (deglata - deglatb) * meterperdeg / imagesizey * dpi / 0.0254

  1. 33.6529242569511deg - 33.13518696069031deg = 0.51773729626079deg
  2. $1 deg * 111319.49079327358m/deg = 57634.2521844373683014174969282m
  3. $2 m / 1536px = 37.52m/px
  4. $3 m/px * (90px/in * 1in/0.0254m) = 132953.03

which gives scale of 1:132953... not close!

units cancel great, can see calculation value not close 250k.

can explain i'm wrong?

edit in case else stumbles upon answer hidden in spec documents cadrg. dpi use cadrg 169. plug in above equation , works great cadrg. need know correct dpi use imagery trying find scale of , above work.

you need longitude because otherwise map distorted. imo try same formula longitude.


Comments

Post a Comment

Popular posts from this blog

c++ - Delete matches in OpenCV (Keypoints and descriptors) -

-
i want check scene image against 2 train images. that, detect features , compute descriptors of both training images. before detecting, computing , matching scene image, delete matches of train1 , train2. because these matches won't facilitate matching of scene image train1 , train2. so, match train1 train2 , vector of matches trainidx , queryidx. how can delete these matches in keypoints-vector , descriptor matrix of train1 , train2? best regards, dwi i have done below: std::vector<cv::keypoint> keypoints[2]; cv::mat descriptor[2]; std::vector< cv::dmatch > matches; /* write code generate keypoints, descriptors , matches here... keypoint[0] -> train image 1 keypoints keypoint[1] -> train image 2 keypoints descriptor[0] -> train image 1 descriptors descriptor[1] -> train image 2 descriptors matches -> matched between train image 1 , 2 */ // logic keep unmatched keypoints , corresponding descriptor
Read more

java - Could not locate OpenAL library -

-
i writing game using slick2d library, uses lwjgl. lwjgl version 2.9.3. using netbeans 8. i tried adding sounds game, example music track on main menu. problem is, exception when run game, despite game still compiling , running except sound of course: sat mar 21 01:23:57 edt 2015 error:could not locate openal library. org.lwjgl.lwjglexception: not locate openal library. @ org.lwjgl.openal.al.create(al.java:156) @ org.lwjgl.openal.al.create(al.java:156) @ org.lwjgl.openal.al.create(al.java:102) @ org.lwjgl.openal.al.create(al.java:206) @ org.newdawn.slick.openal.soundstore$1.run(soundstore.java:295) @ java.security.accesscontroller.doprivileged(native method) @ org.newdawn.slick.openal.soundstore.init(soundstore.java:292) @ org.newdawn.slick.music.<init>(music.java:156) @ org.newdawn.slick.music.<init>(music.java:75) @ view.mainmenu.init(mainmenu.java:58) i didn't include rest of error states error happens in game code. the
Read more

sorting - opencl Bitonic sort with 64 bits keys -

-
i used nvidia sdk bitonic sort , works great me. 32 bits (uint) need ulong keys. have typically 2^14 keys @ time , power of 2. searched on not find kernel designed ulong. i tried modified nvidia sdk bitonic sort using ulong keys not work. kernel not crash after de call clenqueuendrangekernel got error : cl_invalid_command_queue can tell me how modify bitonic sort or radixsort, or can sort ulong keys? i running nvidia quadro 4000 opencl 1.1 cuda 6.5.20 full_profile used original nvidia sdk bitonicsort.cl i used"ulong" keys , value input , ouput instead of "uint" thanks helping i made work-around suit need. used 30 bits of key , 18 high bits of value sorting. changed comparators (2 lines): '#define mask 0xffffc000 // suit need from this: if( (*keya > *keyb) == dir ) this: if(((*keya > *keyb)||((*keya == *keyb)&&((*vala & mask)> (*valb & mask)))) == dir ) it works fine. but, still, it's work-a
Read more