Development of algorithm for automatically generating correted selenographic coordinates and imaging geometry for IIRS/Chandrayaan-2 datasets - standalone application
Description
Imaging InfraRed Spectrometer (IIRS) is a hyperspectral instrument on-board Chandrayaan-2 mission that images lunar surface in the spectral range of 0.8 to 5 µm with a spatial resolution of 80 m from 100 km orbit. Data from this instrument is vital to understand the nature and quantity of hydration features as well as mineralogy over the lunar surface. However, the inaccuracy in orbital parameters determination as well as lack of ortho-rectified products leads to errors in the surface location information provided with the datasets, resulting in variable shifts, systematic as well as non-systematic, in selenographic coordinates. In addition, available IIRS datasets lack systematic information about the viewing geometry (incidence, emission and phase angles), which is limited to the central pixel, erroneous and not in a format that can be readily converted into science-ready datasets. To overcome these limitations, a novel approach has been devised to generate per-pixel viewing geometry. Further, we developed an algorithm to automatically generate an ancillary dataset containing the corrected selenographic coordinates, viewing geometry parameters (such as topographically corrected incidence and emergence zenith and azimuthal angles as well as phase angles) and additional important information of Digital Elevation Model (DEM), slope and aspect to be used in further analysis. We also estimated the shifts and quantified the relative errors in the location and viewing geometry, respectively. A standalone application with an easy interactable Graphical User Interface (GUI), requiring minimal user intervention, has also been developed for easier user interface. Here, this developed app has been shared for users interested in viewing geomtry information for IIRS datasets.
Files
Steps to reproduce
Stepwise guide to run the software: a) Download the app, and the wac zipped folder, unzip the wac folder. It contains WAC mosaic resampled at 80 m spatial resolution. b) Download IIRS data from "https://pradan.issdc.gov.in/ch2/" and unzip the data. b) Download SLDEM 2015 data from "https://imbrium.mit.edu/DATA/SLDEM2015/GLOBAL/JP2/SLDEM2015_512_60S_60N_000_360.JP2" and resample it to 80 m IIRS resolution. Also, remember to scale the values by 0.5 and round it to integer values. Make sure to store it in envi format with 16 bit signed integer format and ending with extension ".img" along with header file. c) Run the app, click on the browse buttons and choose respective datasets. For IIRS data, choose the address of the unzipped folder. d) click on "Run all processes" button and GUI will start running. e) A popup will appear, choose the latitude range within 58 deg N and 58 deg S, and the buffer size or keep as default values. f) Next popup will show the GCP list with listed errors, note the highest number of GCPs to be used and close the window. G) Another pop-up will appear asking the number of GPs to be used, input the number and press okay. h) A window showing the GCPs in base as well as master image connected using multi-coloured lines will be shown, verify the GCPs and close the window. i) A pop up will appear showing whether to use the algorithm identified GCPs or not. Select the relevant option. j) The algorithm will run for some time and will generate the final output.