RadarVolumeExplorer v0.01
==========================

RadarVolumeExplorer is a 3D visualization tool for meteorological radar 
data. It can visualize the scan slices in PPI mode (Flat Model), in CAPPI
mode (Cartesian Model) and in Isometrical View.

0) How does it work?
--------------------

RadarVolumeExplorer has three ways of visualizing volume datasets:

a) Flat Model

In this model, each azimuthal scan of the whole volume dataset is 
visualized as-is in 3-dimensional space, very much like a set of 
PPI (Plan Position Indicator) images.

b) Cartesian Model

In this model, RadarVolumeExplorer generates a set of CAPPI (Constant 
Altitute Plan Position Indicator) images at different heights above the 
radar position which are then visualized as-is in 3-dimensional space.

c) Isometrical Model

This model showcases the main reason why I wrote this program in the 
first place :-)
Radar volume scans consist of a set of data measurements whereby each 
measurement consists of a value and a 3-dimensional polar coordinate:

  (1) Range (in km)
  (2) Azimuth Angle (in degrees)
  (3) Elevation Angle (in degrees)

The problem of visualizing 3D volume scans on the computer screen is very
similar to the situation with CT (Computed Tomography) scans:

The physical scan results in a set of measurements in 3-dimensional space
(a.k.a. voxels). This is also called a "solid model". This solid model 
needs to be transformed into a set of point vectors which form a set of 
triangles which can be rendered directly by a graphics card. This is 
called a "geometric model".

In the field of medical imaging (for example: CT scans), this process of 
transforming the solid model into a geometric model is often done using 
an algorithm called "marching cubes". For more information about the 
marching cubes algorithm, here's an article on Wikipedia:

   https://en.wikipedia.org/wiki/Marching_cubes
   
The big difference between radar volume scans and CT scans is that radar 
volume scans result in 3D polar coordinates (range, azimuth, elevation), 
whereas CT scans result in 3D cartesian coordinates (x, y, z). Therefore,
before the marching cubes algorithm can be applied, the radar volume scan
must be transformed into a cartesian model with a regular 3-dimensional 
grid. RadarVolumeExplorer achieves this by generating a set of CAPPI
(Constant Altitude Plan Position Indicator) images at different 
altitutes, the same as what is done in the "Cartesian Model" of the 
application.
In RadarVolumeExplorer, you can generate a number of such isosurfaces 
with different threshold values, colors and transparencies.

1) Supported Radar Data Format
------------------------------

RadarVolumeExplorer supports polar radar volume scans in HDF5 format 
according to the KNMI v3.6 or the OPERA ODIM 2.2 specifications.

KNMI v3.6 Specification:

   http://publicaties.minienm.nl/documenten/
      update-of-knmi-hdf5-data-format-specification-v3-6

OPERA ODIM 2.2 Specification:

   http://eumetnet.eu/wp-content/uploads/2017/01/
      OPERA_hdf_description_2014.pdf

KNMI (Royal Netherlands Meteorological Institute) provides recent radar 
data from several radars on their FTP server:

   ftp://data.knmi.nl//download/radar_tar_volume_denhelder/1.0
   
When you open a HDF5 radar volume data file and it contains more than one
data moment, the application will let you pick one of the available data 
moments to visualize.

The application comes with a couple of KNMI v3.6 samples.

2) Topographical Data (DEM)
---------------------------

RadarVolumeExplorer supports SRTM30 DEM (Digital Elevation Model) data. 
You can download the DEM slices from

   http://www.dgadv.com/srtm30/

or

   https://dds.cr.usgs.gov/srtm/version2_1/SRTM30/
   
and copy them to the "dem/srtm30" directory of the application. The DEM 
set consists of 28 files with 56250KB each, totalling in about 1.44GB.

3) Geographic Information System Data (GIS)
-------------------------------------------

RadarVolumeExplorer supports ESRI shapefiles in *.shp and *.dbf format 
for displaying points (like places and cities) and polygons (like country
borders) on the map. The application comes with the following shapefiles 
in the "overlays" directory:

   - ger-places.shp|dbf: Places in Germany (Cities, Towns, etc.)
   - nl-places.shp|dbf: Places in Germany (Cities, Towns, etc.)
   - ne_10m_admin_0_countries.shp|dbf: European Country Borders


https://mapcruzin.com/download-shapefile/


Copyright (c) 2018, 2019 by Christian Nowak a.k.a. Creestee
Contact Email: creestee@creestee.com or chnowak@web.de
Website: http://www.creestee.com/
