Raster styling changes with zoom

[tfaulkner92]

I connected to a raster file (ESRI grid - .asc format) and successfully styled the map. I am satisfied with what I see when viewing the map at a high level, but when I zoom in, the styling changes drastically. Zooming in very close eventually begins to show individual grid cells, but this is not useful. Is there a setting that will control this? I do not want the apparent contours of elevation zones to change simply because I zoom in on the data. Attached is a .gif of what I see as I zoom in and then zoom back out.

[ChicagoLooper]

Hi @tfaulkner92 

Thanks for uploading your gif. Sorry, there's no 'setting.'

The ASC format, at least free downloaded files, are typically obtained by satellites orbiting above the earth--miles and miles above the earth.  Your gif shows you are zooming in as tight as 30 feet and relative to the altitude of the satellite, 30 feet is miniscule. that's It's like looking at cars driving by as you stand on the balcony of a 3-story building. The resolution you expect to acquire can't be compared to the satellite precision you see in Hollywood movies.

The free downloadable stuff can't zero in a license plate nor see the peas and carrots on your neighbor's plate as he's eating dinner next to his window.

If you want contours then you're better off downloading contour data as opposed to an ASC grid.

For maximum forum action, you should name the city and state of your target area so the forum can suggest a more practical workflow. 

If your site is flat or gently sloped, an ASC grid nor 10-ft contours may not be useful at the zoomed-in scale you illustrate in your gif. Elevation data in formats in various formats, e.g. laz, tif, DEM, topo contours, can be downloaded from one such as this one >>HERE<<. You might find one that's more suitable for your needs.

[tfaulkner92]

@ChicagoLooper 

Thanks for the quick reply!

I'm with you on the caution of suggesting detail beyond what is practical, but in this scenario, the data came from user-collected survey points (not downloaded from USGS or another site). I converted the data to an ESRI grid with 50x50' grid cell spacing for the purpose of making a map. That being said, I want to be able to inspect the map without having the display change. If a color zone is defined from the data, why can't I simply inspect the limit of that zone? The precision of the data is already understood by those who will be reading this map, but I can't work with a map that is going to dynamically change on me.

Are you aware of a method to permanently draw the zoomed-out map to the screen (preferably as HATCH entities)? That would be ideal for this scenario.

[ChicagoLooper]

@tfaulkner92 

<<...That being said, I want to be able to inspect the map without having the display change. If a color zone is defined from the data, why can't I simply inspect the limit of that zone?

If you want an answer for your issue, can you share your asc? I can't offer a practical workflow without the data.

Do you run Civil3D in addition to Map3D?

[tfaulkner92]

@ChicagoLooper 

Gladly!

Data has been scrubbed for confidentiality, but concept still applies. Values range from ~65 to ~73. I'd like to color the map on 1 unit intervals. I've attached an image showing how I've colored the map.

Seems that I can't directly attach .asc files, so I changed the extension to .txt.

[ChicagoLooper]

That data is useless.

Upload your ASC.

[Pointdump]

Hi Tyler,
Zip your ASC file and then the Forum will accept it.
Dave

[tfaulkner92]

@ChicagoLooper 

Attached in a zipped folder.

[Pointdump · Accepted solution]

Tyler,
Thanks for posting your data.
Yup, in my test, zooming past 1:1740 gets wierd fast. I don't know what can be done about it.
Dave

[ChicagoLooper]

@tfaulkner92 

So you exported an ASC grid from Arc Pro, correct? What data did you use in Arc Pro. That data is important. Can you upload it. The ASC you uploaded isn't georeferenced and could be someplace far, far away. What's your end goal, create a surface? 

When you add your ASC to modelspace, did you assign a coordinate system? If you did, turn on Bing Hybrid so it shows up in the background. Then upload an image with Bing aerial in the background and the ASC on top of it. 

Image-1: ASC using your style. 

Image-1

Image-2: Styled using National Map Palette.

Image-2

Image-3: Another palette.

Image-3

Image-4: Your style, same as first image. Contours can be added using the ASC data (1-foot interval). Map3D Toolset to generate the contours.

Image-4

Notes:

1. Export to ASC again, but this time, give the export a proper projection so it's georeferenced.
2. Use contours, not colors, to analyzes surface elevation. Although colors make a nice presentation, they're better suited as an enhancement or supplement to other, more analytical drawings.

[tfaulkner92]

@ChicagoLooper 

I'm not using Arc Pro, but I do have the ability to export my grid to the Esri grid format. The projection is irrelevant in this case - just assume a local coordinate system.

You showed that you can import the data and apply a coloring style, but do you see the same issue if you zoom in on the data itself?

You suggested using contours rather than colors to analyze the surface, but the colors are intended to be part of the deliverable. My concern is that if the colors are dynamically changing based on zoom level, can I actually trust what I'm looking at? If the colors can't match the contours, regardless of zoom level, I don't think I can work this.

@Pointdump 

Thanks for checking! I'm just surprised to see that it's doing this at all. I suppose it's related to the way the data is being read from the connection and refreshed based on the camera, but it's baffling to have a different answer for a different zoom level.

[ChicagoLooper]

Yes. I see the problem WITHOUT A COORDINATE SYSTEM (you MUST have a projection when you export) your ASC is NOT scaled!!!

AutoCAD does NOT know if it's dealing with inches, feet, millimeters, meters, or kilometers. Since the exported CoordSys will have units, AutoCAD does NOT what size it should be. Zooming into a square that's 10 inches x10 inches is not the same as 10 feet x10 feet and not the same as 10meters x 10meters, etc., etc.

It might even be 10 Degrees x 10 Degrees, as in Lat/Long. You need units to scale properly. Those units will affect how far you zoom-in or zoom-out. Zoom in too tight when you don't have to and you start complaining about the pixels. 

For all YOU  know AutoCAD is zooming into your ASC that's just tiny teeny, itty bitty, 1-square millimeter, as if that's the case, then you're gonna get those zoomed in pixels when you really don't have to be zoomed in that tight.   

Just assume a local coordinate system, you're joking, right? Even a local coordinate systems will have units. What are the units in your secret local CS?

[tfaulkner92]

@ChicagoLooper 

I think you're missing the point here. Data is data. Let it represent any unit that you want. Feet, meters, whatever. If the data has a set value at a grid node, the colors should reflect the value around that grid node . If the colors are changing based on how much you zoom in, then the system is not giving a consistent answer.

I think if you just zoom in on the map, you'll also see the colors change with zoom level. 

[tfaulkner92]

@ChicagoLooper @Pointdump 

One other question - when contours are generated from the data, the contours don't actually line up with the color zones. This also causes some head scratching.

Any ideas? Is that just how ACAD Map handles coloring/contouring?