NEANIAS Gitlab

Commit 6f89e7ed authored by Carlos H. Brandt's avatar Carlos H. Brandt
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Update documents and data description

parent 67405c9c
......@@ -26,6 +26,127 @@ The following links have further information about this dataset:
* PDS node: https://pds-geosciences.wustl.edu/missions/mars_express/hrsc.htm
* ODE: https://ode.rsl.wustl.edu/mars/indexDatasets.aspx
### ODE - PDS
[PDS Geosciences Node]: https://pds-geosciences.wustl.edu/mex/mex-m-hrsc-5-refdr-dtm-v1/mexhrs_2001/
[Browse under orbit 0010]: https://pds-geosciences.wustl.edu/mex/mex-m-hrsc-5-refdr-dtm-v1/mexhrs_2001/browse/0010/
In ODE there is a nice interface to explore the PDS archive they have.
It is a PDS archive.
#### Archive summary
Let's quickly summarize some information ([hrsc_eaicd.pdf) regarding the HRSC
PDS archive regarding name and structure conventions in place.
> All HRSC data belong to one data set. Therefore, the DATA_SET_ID for all data is constant and has the following value: `MEX-M-HRSC-5-REFDR-DTM-V1.0`
The HRSC data are sorted by orbit in the `DATA` directory, each sub-directory is
a "dddd" format number of the orbit in which the data were taken.
The `BROWSE` directory mirrors/mimic the `DATA` structure.
* Filenaming Convention
> The image files in the DATA directories follow this convention:
> ```
> HOOOO_MMMM_DD4.IMG
>
> * OOOO 4 digit orbit number
> * MMMM number of the image in this orbit
> * DD sensor name (can be ND,BL,GR,IR,RE,DT,DA)
> * The ‘4’ indicates the level of processing which is archived in PSA/PDS.
> ```
* Time Standards
> All time information in the data follows the SPICE time standards. Please, see [13], [14], and [15] for details. Within the data products themselves, the time standard used is ET (Ephemeris Time), which is a double precision number of seconds. The starting point for this time is the J2000 epoch.
> (...)
> The main time values are provided in the data product labels,
* Reference Systems
> All latitudes and longitudes are given in degrees, latitudes are planetocentric.
> The level 4 products will be projected onto a SPHERE in authalic/conformal projection (sphere formulae with planetocentric latitude) using radius of the MOLA sphere (3396.0 km) [21,22]:
> * If the latitude center of the image is between -85° and +85°:
> Sinusoidal projection center latitude = 0, center longitude will be determined automatically using an integer value
> * If the latitude center of the image is < -85° or > +85°:
> Stereographic projection, center latitude = +/- 90°, center longitude=0°
>
> We used two different reference bodies [21,22] for the generation of the digital terrain models:
> - MOLA sphere (dt in the filename)
> - MOLA Areoid (da in the filename)
* Geometric Index File
> The Index Directory also contains the Geometric Index File as defined in [7]:
> - geoindex.tab
> - geoindex.lbl
* Browse directory
> The browse directory has sub-directories for every orbit which belongs to the data set, the directory name is the four digits orbit number. The browse images are generated from the origial data using the following steps:
> - reducing the size both in line and sampl direction by a factor of 8
> - conversion to unsigned 8 bit data
> - conversion to raw data
> - conversion to jpeg using the UNIX program cjpeg with the highest compression quality (100)
> The filenames of the browse files are the same as the original image files, the extension is changed from IMG for the image files to JPG for the browse files.
> The browse directory also contains a PDS labels for every browse image.
* Data directory
> The Data Directory contains sub-directories for every orbit which is part of the data set, the diretory names are the four digits orbit number. The delivery contains level-4 data for the nadir sensor and the four color sensors. It also contains Digital Terrain Models (DTMs) with two different reference bodies [21,22]:
> - MOLA sphere (dt in the filename)
> - MOLA Areoid (da in the filename)
* Software
> The HRSC processing software was developed in the VICAR environment [12]. VICAR was developed by NASA/JPL and was used for the processing of camera data from many planetary missions (e.g. Viking, Galeileo). The data processing team at DLR in Berlin developed specific modules to process the HRSC data.
> These modules perform the following steps:
> - remove all telemetry headers from the data
> - sort the data by sensor and combine the image data with the housekeeping data
> - decompression of the data
> - radiometric calibration of the data
> - calculation of the footprints for every image
> - improvement of orbit and attittude data [19,20]
> - generation of Digital terrain Models and Orthorectification of image data [19,20]
#### Exploring the archive
Our interest now is to access the Level-4, DTM data; Which is under
`MEX-M-HRSC-5-REFDR-DTM-V1.0/MEXHRS_2001`.
Same archive/content -- to double check -- of [PDS Geoscience Node].
A `BROWSE` directory is available, which allows us to quickly check what is the
data to expect.
[Browse under orbit 0010] and we see the corresponding list of files:.
```
h0010_0009_bl4.jpg
h0010_0009_bl4.lbl
h0010_0009_da4.jpg
h0010_0009_da4.lbl
h0010_0009_dt4.jpg
h0010_0009_dt4.lbl
h0010_0009_gr4.jpg
h0010_0009_gr4.lbl
h0010_0009_ir4.jpg
h0010_0009_ir4.lbl
h0010_0009_nd4.jpg
h0010_0009_nd4.lbl
h0010_0009_re4.jpg
h0010_0009_re4.lbl
```
As explained in [hrsc_eaicd.pdf], the substring `0009` correspond to number os
that image in this orbit (`0010`); While `{bl,da,dt,gr,ir,nd,re}4` correspond to
the image device or model used to create the (`.jpg`) respective product;
`4` corresponds to the level of the product.
The image type infixes mean as follows:
* `BL`: Blue sensor
* `GR`: Green sensor
* `IR`: Infrared sensor
* `ND`: Nadir sensor
* `RE`: Red sensor
* `DA`: DTM-areoid
* `DT`: DTM-sphere
What we want is primarily the Nadir (ND) observations, and the DTM (DA and DT)
products.
### Keywords
......
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