Commit 74327634 authored by Daniel Scheffler's avatar Daniel Scheffler
Browse files

Revised the tutorial and added a missing figure.


Signed-off-by: Daniel Scheffler's avatarDaniel Scheffler <danschef@gfz-potsdam.de>
parent 4d169f92
Pipeline #5641 canceled with stage
in 11 minutes and 21 seconds
......@@ -58,7 +58,7 @@ is given `here <https://gitext.gfz-potsdam.de/EnMAP/GFZ_Tools_EnMAP_BOX/EnPT/raw
.. note::
The contents this zip-archive may change in future.
The contents of this zip-archive may change in future.
Open QGIS_, start the EnMAP-Box_ and load the :file:`ENMAP*L1B*-SPECTRAL_IMAGE_VNIR.GEOTIFF` and
......@@ -67,15 +67,14 @@ general handling instructions regarding the EnMAP-Box_ are given in `Exercise A
.. _`Exercise A of the EnMAP-Box tutorials`: https://enmap-box.readthedocs.io/en/latest/usr_section/application_tutorials/urban_unmixing/tutorial.html#exercise-a-urban-land-cover
Unfold the respective entries in the **Data sources** panel to explore some metadata of both images. As apparent from
there, both images have 1000 x 100 pixels in x- and y-direction. The VNIR image contains 88 and the SWIR contains 130
spectral bands. Both images have no coordinate reference system (CRS). This is because EnMAP Level-1B data are provided
in sensor geometry.
Unfold the respective entries in the **Data sources** panel to explore some metadata of both images. Both images have
1000 x 100 pixels in x- and y-direction. The VNIR image contains 88 and the SWIR contains 130 spectral bands. Both
images have no coordinate reference system (CRS). This is because EnMAP Level-1B data are provided in sensor geometry.
To visualize the first spectral band of the VNIR hyperspectral image, unfold the **Bands** entry of the VNIR image in
the **Data sources** tab, right-click on **Band 01:B1** and press **Open in new map**. Then click the Spectral Library
icon in the EnMAP-Box toolbar to open a new Spectral Library window and click somewhere into the visualized image in
the Map window. This makes the corresponding spectral signature show up in the Spectral Library window.
the **Map** window. This makes the corresponding spectral signature show up in the **Spectral Library** window.
.. image:: img/tut__enmapbox_l1b_vnir.png
......@@ -83,10 +82,10 @@ Open the first band of the SWIR image and visualize any SWIR spectral signature
.. image:: img/tut__enmapbox_l1b_swir.png
With regard to the spectral signature plot, it is noted that EnMAP Level-1B data contain top-of atmosphere radiance
spectra whereas each spectral band is scaled according to specific gain and offset values given in the image metadata.
The visualized spectra can therefore NOT directly be interpreted as top-of-atmosphere radiance but have to be converted
first. Even if all bands were equally scaled, the spectra would not be comparable to other hyperspectral EO data
With regard to the spectral signature plot, it is noted that EnMAP Level-1B data contain top-of-atmosphere radiance
spectra, with each spectral band scaled according to specific gain and offset values given in the image metadata.
The visualized spectra can therefore NOT directly be interpreted as top-of-atmosphere radiance but must first be
converted. Even if all bands were equally scaled, the spectra would not be comparable to other hyperspectral EO data
because they are still affected by numerous spatio-temporal varying effects, e.g., originating from the atmospheric
state at the acquisition time.
......@@ -97,8 +96,8 @@ vertical striping effects, i.e., dead image columns.
.. image:: img/tut__enmapbox_l1b_vnir_swir_shift_deadpix.png
To sum up, EnMAP Level-1B data cannot directly be used for downstream remote sensing applications due to the following
characteristics:
To sum up, EnMAP Level-1B data cannot be directly used for downstream remote sensing applications due to the following
reasons:
- separate VNIR and SWIR detector images
- images provided in sensor geometry, i.e., without coordinate reference system (CRS)
......@@ -106,6 +105,7 @@ characteristics:
- VNIR and SWIR images do not show the same spatial extent (offsets in along- and across-track direction)
- image artefacts such as vertical striping due to dead pixels
- spectral information is affected by various spatio-temporal effects, e.g., originating from the atmospheric state
- some sensor-induced effects that are not directly visible (spectral smile, keystone, ...)
Generate Level-2A data using EnPT
......@@ -116,7 +116,7 @@ raw format to geometrically and atmospherically corrected bottom-of-atmosphere r
:ref:`algorithm_description` section of this documentation for more information on the underlying algorithms.
Open the EnPT GUI to run the processing chain. You can find it here:
:menuselection:`QGIS 3.xx --> EnMAP-Box --> Processing Toolbox --> Pre-Processing --> EnMAP processing tools algorithm`.
:menuselection:`QGIS 3.xx --> EnMAP-Box --> Processing Toolbox --> EnMAP-Box --> Pre-Processing --> EnMAP processing tools algorithm`.
.. image:: img/tut__screenshot_enpt_enmapboxapp.png
......@@ -125,8 +125,8 @@ above at the parameter **L1B EnMAP image** and check that the **Anaconda root di
Anaconda directory which contains the `enpt` Python environment (see :ref:`installation`). All other parameters are
set to a default or not strictly needed to generate Level-2A data. However, they may improve the output quality.
Press the **Run** button to start the processing. The current status is shown in the **Log** panel. After processing,
the output directory is also indicated there.
Press the **Run** button to start the processing. The current status is shown in the **Log** panel and the QGIS Python
console. After processing, the output directory is indicated in the Log panel.
Inspect the Level-2A data and compare them with Level-1B
......@@ -143,15 +143,15 @@ other files, such as metadata, quality layers, etc.:
Load the :file:`ENMAP*L2A*-SPECTRAL_IMAGE.GEOTIFF` into
the EnMAP-Box_. Unfold the entry in the **Data sources** panel to explore some metadata of the Level-2A EnMAP-image.
The image has a dimension of 959 x 311 pixels in x- and y-direction and contains 218 bands. The different image
The image has a dimension of 972 x 378 pixels in x- and y-direction and contains 218 bands. The different image
dimensions compared with Level-1B data are due to the geometric correction / orthorectification applied by EnPT.
Furthermore, the image is now projected in WGS84 / UTM zone 32N.
Visualize the first band of the image and open a Spectral Library window as described above. The spectral information
now contains atmospherically corrected bottom-of-atmosphere reflectance data. The two detector images have been merged
so that their spectral information can now be used together. Spatio-temporal variable disturbances to the spectra have
so that their spectral information can now be used together. Spatio-temporal varying interferences on the spectra have
been corrected as far as possible.
.. image:: img/PLACEHOLDER
.. image:: img/tut__enmapbox_l2a_output.png
The generated EnMAP Level-2A data can now be used for subsequent remote sensing applications.
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