I note that both GRT and AFS do not have a quadrilateral grid superimposed over their synthetic vision view. On the other hand Dynon, MGL, and perhaps Garmin, have a grid.
I've had the opportunity to personally see two high end certificated SV systems and both had the grids.
My opinion is that a grid allows for superior terrain depth perception, particularly in a relatively flat environment. The downside is that it presumably requires more processing power.
I also note that Dynon's superimposed quadrilateral grid uses an alternating colour mode (eg. the green areas have alternating dark and light green quadrilaterals). This seems to provide even better depth perception.
I think those guys at Dynon are really doing their homework on the "Skyview" system.
Yes you are correct. Garmin has the grid as well.
You need some form of grid for an EFIS to allow instant orientation (the grid would be aligned lat/long) and it allows instant distance judgement.
It also enhances terrain. The trouble with terrain is, unless you pose it (Airshow favourite) it does not look good as you are working with only slight differences in color gradients or have to add "fog" to enhance distance. All of this does not work well if you have a lot of ambient light shining on the display surface.
You may have noticed that we have now gone a bit further as well and are showing important features like highways, major roads, rivers and so on as well on the 3D SV. In addition you can simply switch that to a FLIR camera with AHRS grid overlay so you have the best of both (or even just a normal cheap bullet camera - just for the fun of it).
The grid does not really add to processing power requirements. The texture mapping (using bilinear filtering) is far more hungry for processing power and really has to be done in a dedicated graphics processor if you want any sort of acceptable frame rate.
The idea behind SV is to present an abstraction of the terrain and important features - you don't want to have real looking terrain like you have with a flight simulator - after all this is not intended to simulate but to be a real World tool for a real pilot. It needs to convey information in a clear and instantly recognizable manner.
Probably the most convincing way to explain this is if you connect one of our EFIS's to a flight simulator (Microsoft's work just fine for this).
The "outside view" on the flightsim looks close to real while the corresponding terrain view on the EFIS looks abstract. But while "flying" in mountainous terrain the EFIS shows a much clearer and defined picture of what matters (and as extra bonus also gives a much wider field of view thanks to trickery).
For those that do not agree, we have a little present as well - you can view satellite images in 3D on the SV just like Google Earth. Free.
Rainier
CEO MGL Avionics
