Questions about resolution and images

  • These are rather long and detailed questions, but if anybody can answer even one of them I'd be very grateful!

    1. FSET resolution 3 is 4 m/Pix and resolution 4 is 4'm/Pix. What is the difference?

    2. What is the resolution of the best Virtual Earth images? Since they can be captured at 0.25 m/Pix, I assume there are many places where it is at least as good as that?

    3. In another post I argued that a level 15 tile is about 800 x 800 metres. Given that tiles of all levels are 2048 x 2048 pixels it follows that each level 15 pixel is about 40 cm x 40 cm. So level 15 is needed to fully take advantage of FSET resolution 0 (0.5 m), as shown in @Rodeo's chart in another thread. That being the case, my question is about the justification for capturing FSET images at a resolution of -1 (0.25 m). My feeling is that, although the final resolution will only be 0.4 m, the quality of information that goes into each pixel will still be better if the FSET resolution is 0.25 m. Does that make sense? [The downside, of course, is that it tales 4x as long to capture the info from FSET.]

    4. When I look down (using FSET -1, level 15) I can see sheep in the fields. If the resolution is 40 cm, that means each sheep is an elongated blob of about 1 x 3 pixels - 0.4 x 1.2 metres being my estimated size for a sheep! So far, so good. What puzzles me, however, is that I have the impression that I can see detail smaller than a sheep - i.e. the detail looks smaller than the width of a sheep. Examples are: the white lines on roads (about 15 cm wide?), power cables between pylons (about 5 cm wide?), etc. If there is a 15 cm white line on blackish asphalt I would expect a greyish pixel to be produced with a width of 40 cm. My brain then interprets this as (a) white and (b) narrower than a sheep because it knows that, in reality, a road marking is white and narrower than a sheep. Is this what's happening - or is there something I don't understand about images?

    5. Still on the subject of being tricked by the brain ..... Using FSET -1 and level 15 low buildings and trees look 3D to me above about 100 metres. I can't decide whether this effect is enhanced by shadows, or whether it would be the case even without shadows in the FSET images. (Unfortunately this doesn't work for taller structures above about 2 storeys, which look flattened from any altitude.) So it seems to me that I only need cultivation when I'm below 100 metres or above a town where there are taller buildings (or if I need night lighting effects etc - or if the native FSET quality of the image isn't good enough to produce the 3D effect.) Is this how other people see it, or is it just me?

    6. The Oculus Rift has a resolution of 1080 x 1200 and a field of view of 110 degrees. This means that the angular resolution is about 0.1 degrees. (Compare this with the angular resolution of the unaided eye, which is about 0.02 degrees or 0.0003 radians. So the Rift would need to improve its resolution by a factor of 5 in order to be equivalent to normal vision.) 0.1 degrees corresponds to a 40 cm (level 15) pixel viewed from a height of about 230 metres (800 feet). So, if you're using the Rift, it's worth having level 15 tiles at any altitude below 230 metres. Also it means that you wouldn't really want to see any lower level tiles (14, 13, etc) below about 230 metres. Is there a danger that these lower levels will kick in when you don't want them (i.e. below 230 metres) thus lowering the optimum resolution? (Given that I only fly low and slow I'm trying to optimise my scenery for low altitude.)

    Edited 6 times, last by Ian C (December 3, 2017 at 7:09 PM).

  • Hi Ian,

    This is just my observations from doing scenery here the past couple of weeks. So take it with a grain of salt. :)

    1. Good question, I was wondering the same thing.

    2. I have seen mostly 0.5m resolution in my area, I assume that some areas are .25 though.

    3. I think that is correct. I download everything at .5m, but then convert it to level 14 or 1m resolution. It only makes sense that the better res you start with, the better you end with, even if down-scaling. I could be wrong, but it makes sense to me. Having done some areas at level 15, I am hard pressed to tell the difference between 14 and 15. Even 2m resolution at level 14 seems pretty darn good to me. Most of the areas I have done are .5 downloaded, then Level 14. Areas further out I have done at 1m then level 14. Level 15 just does not make sense in my mind, between the time it takes, and size for such little visual difference.

    4. I think on smaller things like stripes, lines etc. even though they are smaller than .5, you get "bleed through" of color especially bright colors that give impression of them being larger. Also, the images may be at higher than .5 or .25. I am not sure how they are calculating it. It probably depends on a number of factors.

    5. For sure. Even when I cultivate an area, sometimes I need to look twice and question if it is a 3D building, or just the image that looks really good. The shadows do play a part I think. Overall a good optical illusion that makes a 2d image look 3d.

    6. I don't know the answer to that, but I have not found a time where it looks good, and then switches to looking bad. I think the transition to and from levels is pretty seamless. The main thing that distracts me is still the Screen Door Effect in the Rift. They claim it is pretty much gone, but it still bugs me. When they hit the market, I am going to try one of the PiMax 8K units. I just hope they implement ASW. I know some don't care for ASW, but for me it makes buttery smooth image movements.


  • Hi Andrew

    Thanks for your reply. It's great to get another perspective on these things. Regarding question 3, I guess the principle is similar to increasing the render scale factor in the VR settings. The improvement can only be marginal, but it is there. (Not that increasing RSF works for me, but that's another matter!) Like you, I've never noticed any step change to a lower resolution when gaining altitude so you're probably right on that one. The screen door effect is indeed a distraction - mostly, for me, when looking at the distant skyline.

    So far I've created 23 GB of tiles converting an area about the size of an English county! So I can see myself having to invest in extra drives if I carry on at this rate.