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  1. ![Aptdec logo](textlogo.png)
  2. Copyright (c) 2004-2009 Thierry Leconte (F4DWV), Xerbo (xerbo@protonmail.com) 2019
  3. ## Description
  4. Aptdec is an FOSS program that decodes images transmitted by NOAA weather satellites. These satellites transmit continuously (among other things), medium resolution (1px/4km) images of the earth on 137 MHz.
  5. These transmissions could be easily received with an simple antenna and cheap SDR. Then the transmission can easily be decoded in narrow band FM mode.
  6. Aptdec can convert these audio files into .png images.
  7. For each audio file up to 6 images can be generated:
  8. 1. Raw image: contains the 2 transmitted channel images + telemetry and synchronization pulses.
  9. 2. Calibrated channel A image
  10. 3. Calibrated channel B image
  11. 4. Temperature compensated IR image
  12. 5. False color image
  13. 6. Layered image, boosts cloud visibility
  14. The input audio file must be mono with a sample rate in the range of 4160-62400 Hz, lower samples rates will process faster.
  15. Aptdec uses `libsndfile` to read the input audio, so any format supported by `libsndfile` may be used (however it has only tested with `.wav` files).
  16. ## Compilation
  17. Aptdec is portable since it is written in standard C.
  18. It has successfully compiled and ran on Debian with both `gcc` and `clang` and will most likely work on any Unix platform.
  19. Just edit the Makefile and run `make` (no configure script as of right now).
  20. Aptdec uses `libsndfile`, `libpng` and `libm`.
  21. The `snd.h` and `png.h` headers must be present on your system.
  22. If they are not on standard path, edit the include path in the Makefile.
  23. ## Usage
  24. To compile
  25. `make`
  26. To run without installing
  27. `./aptdec [options] audio files...`
  28. To install
  29. `sudo make install`
  30. To run once installed
  31. `aptdec [options] audio files...`
  32. To uninstall
  33. `sudo make uninstall`
  34. ## Options
  35. ```
  36. -i [r|a|b|c|t|l]
  37. Output image type
  38. Raw (r), Channel A (a), Channel B (b), False Color (c), Temperature (t), Layered (l)
  39. Default: "ab"
  40. -d <dir>
  41. Images destination directory (optional).
  42. Default: Current directory
  43. -s [15|16|17|18|19]
  44. Satellite number
  45. For temperature calibration
  46. Default: "19"
  47. -e [c|t|h]
  48. Enhancements
  49. Contrast calibration (c), Histogram equalise (h), Crop Telemetry (t)
  50. Defaults: "ct"
  51. -c <file>
  52. Use configuration file for false color generation.
  53. Default: Internal defaults
  54. ```
  55. ## Output
  56. Generated images are outputted in PNG, 8 bit greyscale for raw and channel A|B images, palleted images for temperature and GVI false color, 24 bit RGB for false color.
  57. Image names are `audiofile-x.png`, where `x` is:
  58. - `r` for raw images
  59. - Sensor ID (1, 2, 3A, 3B, 4, 5) for channel A|B images
  60. - `c` for false color.
  61. - `t` for temperature calibrated images
  62. - `l` for layered images
  63. Currently there are 3 available enhancements:
  64. - `c` for calibration, on by default
  65. - `t` for crop telemetry, on by default, only has effects on raw images
  66. - `h` for histogram equalise, make the darkest color black and the brightest white
  67. ## Example
  68. `aptdec -d images -i ab *.wav`
  69. This will process all `.wav` files in the current directory, generate calibrated channel A and B images and put them in the `images` directory.
  70. ## Further reading
  71. [https://noaasis.noaa.gov/NOAASIS/pubs/Users_Guide-Building_Receive_Stations_March_2009.pdf](https://noaasis.noaa.gov/NOAASIS/pubs/Users_Guide-Building_Receive_Stations_March_2009.pdf)
  72. [https://web.archive.org/web/20141220021557/https://www.ncdc.noaa.gov/oa/pod-guide/ncdc/docs/klm/tables.htm](https://web.archive.org/web/20141220021557/https://www.ncdc.noaa.gov/oa/pod-guide/ncdc/docs/klm/tables.htm)
  73. ## License
  74. See LICENSE.