SAC-PSG-CIGI Archives

October 2016

SAC-PSG-CIGI@DISCUSSIONS.SISOSTDS.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Curtis Schroeder <[log in to unmask]>
Reply To:
SAC-PSG-CIGI <[log in to unmask]>
Date:
Wed, 5 Oct 2016 15:26:49 -0400
Content-Type:
text/plain
Parts/Attachments:
text/plain (17 lines)
This PCR was proposed at the September 2016  CIGI PSG meeting, but in actuality has a longer history. For many years now, the CIGI SG/PDG/PSG has been aware that users wanting to use a Cartesian coordinate system had to seriously hack the CIGI ICD to accomplish their needs. Work-arounds have included a top level "world" entity and then all simulation entities are created and manipulated as child entities or if the user had access to the IG source code then passing (X, Y, Z) using (Lat, Lon, Alt) in the Entity Control packet. We can and should do better to support the simulation community and we also need to look forward to supporting simulations on other planetary bodies. In my own work, I have recently encountered a simulation project using ECEF. It would be nice to use this coordinate system natively with CIGI, instead of the host needing to jump through hoops to convert to Geodetic.

Late in the drafting of CIGI 4.0, I started to build a possible enhancement for this, but it grew too large in scope too be considered for inclusion. One of the ideas I had was to build upon SISO's SEDRIS SRM and its Spatial Reference Frame Templates. My intent was to keep Geodetic the default coordinate system for backward compatibility, but allow the host to request other coordinate systems using the approved SRM SRFT codes. New coordinate systems could be added through the documented SRM process. A predefined IG status flag would be added for the IG to signal the host when it did not support the requested SRFT. It would be up to each IG vendor whether they wanted to investigate adoption of the open source SRM transformation library or develop their own.

This looked pretty straightforward, until I started thinking about space simulations. A CIGI host might need to use different coordinate systems for different entities, e.g. a space station or satellite orbiting the Earth while another entity orbits the Moon. Indeed, a spacecraft traveling to the Moon would need to change coordinate systems during its journey. The big question was whether the Entity Definition needed to be enhanced to allow the coordinate system to be selected on a per entity basis or only have a single, global coordinate system used by all entities? This is where I stopped developing the idea in 2013.

So, now you have the background. Please discuss this idea in this forum thread.

Best regards,

Curt Schroeder

########################################################################

To unsubscribe from the SAC-PSG-CIGI list, click the following link:
https://discussions.sisostds.org/index.htm?SUBED1=SAC-PSG-CIGI&A=1

ATOM RSS1 RSS2