Opened 16 months ago

Last modified 16 months ago

#168 new enhancement

Addition of grid mapping for radar and lidar data in radial coordinates — at Version 6

Reported by: mikedixon Owned by: cf-conventions@…
Priority: medium Milestone:
Component: cf-conventions Version:
Keywords: radar lidar grid mapping Cc:

Description (last modified by mikedixon)

Introduction

Radars and Lidars sample the atmosphere using a pulse of energy transmitted from an instrument along a line of sight away from the instrument, with a specified beam width (solid angle). The received signal is sampled over time, which allows for the estimation of the distance of the target from the instrument.

The raw data is stored in radial (polar) coordinates. The location in space, especially in the vertical, is dependent on the propagation of the energy through the atmosphere. Vertical gradients of the index of refraction lead to complexities in determining the height of the target.

The organization and interpretation of radial data of this type is not supported by any of the standard grid mapping types currently supported by CF.

Therefore, in order for the CfRadial? radar and lidar format to be formally recognized by the CF user community, we are proposing the addition of a grid mapping specifically for radar and lidar data.

Proposed grid mapping name

We propose the use of the name “radar_lidar_radial_scan”.

Grid mapping parameters

The following example from a CfRadial? file shows the proposed parameters:

grid_mapping:grid_mapping_name = "radar_lidar_radial_scan" ;
grid_mapping:longitude_of_projection_origin = -104.545806884766 ;
grid_mapping:latitude_of_projection_origin = 39.7866401672363 ;
grid_mapping:height_of_projection_origin = 1709. ;

The latitude and longitude are in degrees.

The height is in meters MSL.

The height_of_projection_origin parameter is analogous to the perspective_point_height in the vertical perspective projection.

The document is maintained at:

https://github.com/NCAR/CfRadial/tree/master/docs

Change History (7)

Changed 16 months ago by mikedixon

Radar Lidar Radial Scan Grid Mapping Proposal

comment:1 Changed 16 months ago by mikedixon

  • Description modified (diff)
  • Keywords radar lidar grid mapping added

comment:2 Changed 16 months ago by mikedixon

  • Priority changed from high to medium

comment:3 Changed 16 months ago by mikedixon

  • Priority changed from medium to high

comment:4 Changed 16 months ago by mikedixon

  • Priority changed from high to medium

comment:5 Changed 16 months ago by jonathan

Dear Mike

Thanks for your proposal. It would probably encourage discussion if you could put the text in this ticket. That's more accessible than a linked PDF or GitHub, because the ticket is distributed to everyone by email in plain text. We may change to using GitHub instead of trac, but we're not yet technically set up for that. It's being worked on.

If I understand correctly, this proposal is about recording the conversion of polar coordinates (range and angle) to geolocated XYZ coordinates. Is that right? The conversion depends on measured and variable physical quantities, so it's not like other conversions, which depend on geometry. Therefore I'm not sure it's really like a grid mapping. However I understand that you do need to record the geolocating coordinates. Can they be stored as 2D auxiliary coordinates which are functions of range and angle? That's a general CF mechanism which doesn't depend on grid mapping.

Best wishes

Jonathan

comment:6 Changed 16 months ago by mikedixon

  • Description modified (diff)
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