Topic: What is ArcGrid Metadata file?

[dfarris75]

I'm downloading data from USGS and I see 1" NED Elevation file that says ArcGrid Metadata file. I connected to it in Map and it looks like just a big hatched square. I'm not familiar with this type of data.

Please help.

[mjfarrell]

that would be point data from which one could build a GRID surface...

IF one wanted to

[dfarris75]

Ooo me likes the sound of that, but... How the heck do I build a surface from points that are in a file referenced via data connect? I shall check the help file.

[dfarris75]

I also see these available:

       1" NED
       1/3" NED
       1/9" NED
       SRTM Finished 3 arc sec
       SRTM Finished 1 arc sec

1.) The smaller the number the more accurate right?

2.) What is SRTM Finished...?

[dfarris75]

Apparently the data is coming in from a different zone because when I zoom extents it goes way out, but I am unable to locate where it is. Is there a "zoom to" option somewhere that I don't see?

[dfarris75]

I was able to find it finally. There are several .adf files which I guess is the surface. The MetaData is seemingly just the hatched square and it falls into place, but the .adf files come in way down south for some reason. Oh I just got this message...

  WARNING: The problems below were found applying style(s) to element DataConnectSurface:
  There are no grid data in this element.
Failed to get bands data.
ReadNext must be called before fetching data.
There is no data in the extent of current map.
Coordinate transformation failed for this feature.
WARNING: The problems below were found applying style(s) to element DataConnectSurface:
There are no grid data in this element.
Failed to get bands data.
ReadNext must be called before fetching data.
There is no data in the extent of current map.

I guess I'm missing a step or something.

[dfarris75]

Here's what I see when I zoom in to it.

[mjfarrell]

Ooo me likes the sound of that, but... How the heck do I build a surface from points that are in a file referenced via data connect? I shall check the help file.

Create Surface change type to  (GRID)


Or one might build a TIN surface using the points in that file via Points>>Import Points
>>External Project Database...

[dfarris75]

It asks for a .mdb file and there isn't any of them in the dataset.

[mjfarrell]

the default is .MDB however it will accept other ASCII data files...
use the files of type option...

[mjfarrell]

and or you may have to perform a Query against the attached data, inserting points and then use those point objects within the terrain model...


may I see a copy of the entre data set this file is part of?

[dfarris75]

Sure Mike. I'll send it off to you in the am.

[mjfarrell]

Go to this page: http://egsc.usgs.gov/isb/pubs/factsheets/fs14899.html

The NED will be delivered in the Spatial Data Transfer Standard (SDTS) raster profile. The spatially referenced metadata will be delivered in SDTS topological vector profile. Other formats may also be supported. An Internet browse of NED shaded-relief imagery with vector reference information will be provided as an aid to ordering. A customer can identify the requested area graphically through the Internet browser. That area of interest will be extracted from the NED and from the spatially referenced metadata and formatted for delivery. The data will be available to download from the Internet using file transfer protocol or on standard distribution media. As more information on the NED becomes available, it will be accessible through the Internet at gisdata.usgs.gov/ned.


I do not think this metadata is yet available in SDTS so one will not be able to build a surface from the NED product...at this time.

One would still want to get the DEM file...

Further in that page also states:

A. ArcGrid is an Arc/Info proprietary format. Some other software packages can read the ArcGrid format. Customers who specify ArcGrid will be delivered a workspace. The workspace is not tarred or gzipped.


Testing seems to suggest MAP does NOT support this format.

[dfarris75]

Why then was I able to import it and get that green blob of topo to display; only in the wrong position within the coordinate zone?

[dfarris75]

I just started a new blank dwg with no coordinate system/zone applied, attached to the data, both the shape file METADATA and the Raster/Surface files (.adf files). Both attached exactly on top of one another. Yesterday when working in my dwg they came in different places. I guess I had assigned a zone somewhere.

If this data is attaching it has to be readable/importable by Map. Not sure.

If I understand correctly I should be able to product contours from this though.

[dfarris75]

http://map3d.wordpress.com/2007/12/19/surface-from-ned-files/

[dfarris75]

OK I got that to work out wonderfully so now if I could just figure out what was going on with the zone I think it would work great!

Now my question is, how to I take it from NAVD88 to NGVD29???

[dfarris75]

In the tutorial the guy said that the poly's would show zero elev., but the object data would be there so you could query them in and do a alter props to get them @ elev. When I look at these contours they are nothing but flat 2d poly's and have no object data attached...?

[mjfarrell]

In the tutorial the guy said that the poly's would show zero elev., but the object data would be there so you could query them in and do a alter props to get them @ elev. When I look at these contours they are nothing but flat 2d poly's and have no object data attached...?

Once you import the sdf file you will have polylines and object data attached to them, if you check the properties of one you notice it is at an elevation of “0” but the object data has the correct elevation listed. At this time save the drawing and close it out. We need to attach it to another new drawing and perform an alter-property query to alter the polylines elevation. So open a new drawing again and make sure the map task pane is open. Attach the saved drawing (the one you just saved and closed) using the map task pane. Now perform an alter-property query to set the polylines on their correct elevation

[mjfarrell]

what's cool about this question; is that NO you can NOT build the surface file directly from the NED file.
however I did learn something new in the process of discovery...

[dfarris75]

Care to share it with us Michael? :love:

[dfarris75]

I'm still lost with these. I'm trying out the NED's as well as the SRTM's. My lack of knowledge and understanding with coordinate zones obviously hinders me.

The NED is NAD83. My dwg is set up for FL83-EF (NAD83 Florida State Planes, East Zone, US Foot). Should the NED come into this file on target or what because it doesn't? Is there some other zone I need to use for the NED's?

The SRTM is WGS84, but when I go to set up my dwg there isn't one that is just WGS84. There's a category of UTM, WGS84 Datum and there's a category of World/Continental, both of which have several zones based on WGS84, but I have no idea which one to use.

Please help; educate.

[mjfarrell]

process

New MAP drawing for EACH data source
Use the MAP>>Tools>>Assign Global Coordinate System
Set the CS to match what you know about your soure(s)
Import a datasource, and Save the file for each of your data sources.


Open a NEW Map Drawing, Assign the CS you want or need to use.

use Map>>Drawings>>Define/Modify Drawing set.
Attach the file(s) you made above for each of your data sources.

When you perfom a Map>>Query, Map will (should) then perform the required transformations upon import of the queried data.

(where is my tkt to FLA?)