Re: Pixelated, Regional Topograpy Data

I forgot to mention that we now combine the SRTM land data with the ASTER d=
ata which is also available for free. Outside of the US, the ASTER data is,=
 as I recall, the highest generally available resolution, however it is noi=
sy; e.g.; a tile near the Galapagos has a few points indicating ~7,000m ele=
vation on Isla Darwin.

We take all the land data we can get easily and block median it together fo=
r that reason. Simply taking an average would not work well. And the GMT to=
ols are fast so the extra computer time is negligible=85

-jj


On Aug 11, 2014, at 10:38 AM, JJ Becker <[email protected]<=
mailto:[email protected]>> wrote:

I make the SRTM30_PLUS file(s) that were mention. If you=92d like to make y=
our own at a higher resolution here is what I do:

a bit of byte swapping on the HGT format file(s),
(optionally cat several altogether in a tmp file),
(optionally) block median the small tiles together to get the final resolut=
ion you would like,
and grid.


grd2xyz $cgiar -s -bo3 -V |
blockmedian -bi3 -bo3 -I$resolution -R$minX/$maxX/$minY/$maxY -C -V | \
xyz2grd -bi -G$grd  -R$minX/$maxX/$minY/$maxY -I$resolution -V


The block median options can be used to handle the possibly troubling issue=
s arising from the question of what location to pick when selecting the med=
ian height from a cloud of neighboring points (aka the center of the down s=
ampled pixel, the average location of the cloud, the location whose height =
happens to be the median, etc=85)

-jj

On Aug 9, 2014, at 3:13 PM, Gregory (Greg) Brenn <[email protected]<ma=
ilto:[email protected]>> wrote:

Ok,

That's great.  I downloaded an unzipped .hgt files, so what do you think wo=
uld be the best way to convert the .hgt files (I have 4 that I want to conv=
ert) into .grd files, then stich those files together?  Could I use xyz2grd=
 and then use grdpaste?

Thanks a lot for your help.
Greg


On Sat, Aug 9, 2014 at 2:44 PM, Fielding, Eric J (329A) <eric.j.fielding@jp=
l.nasa.gov<mailto:[email protected]>> wrote:
Yes, as Walter mentioned, the SRTM 3-arcsecond (~90 m) digital topography
is available for most of the Earth (up to 60 degrees N & S latitudes), and
it is much higher resolution than the ETOPO1 data that is 1-arcminute or
about 2 km spacing. The latest release is SRTM version 3.0. The Open
Topography website has a new service that will assemble the data and
provide the output in three formats
(http://www.opentopography.org/index.php/news/detail/srtm_version_30_global
_90m_and_united_states_30m_elevation_data_now_availab/<http://www.opentopog=
raphy.org/index.php/news/detail/srtm_version_30_global_90m_and_united_state=
s_30m_elevation_data_now_availab/>). The GeoTIFF files
are easy to convert to GMT .grd files with GDAL.

++Eric Fielding


-----Original Message-----
From: "Walter  Smith  (HF)" <[email protected]<mailto:walter.hf.smit=
[email protected]>>
Reply-To: World-Wide GMT Usage and Help Mailing List
<[email protected]<mailto:[email protected]>>
Date: Saturday, August 9, 2014 11:04 AM
To: "[email protected]<mailto:[email protected]>" <GMT-HELP=
@LISTS.HAWAII.EDU<mailto:[email protected]>>
Subject: Re: [GMT-HELP] Pixelated, Regional Topograpy Data

>=B3pscoast=B2 is defaulting to a low resolution coastline. Try adding -Df =
or
>check the usage message to get your highest option.
>
>There is higher resolution topography than ETOPO1, such as SRTM3. You=B9ll
>have to search around and you may have to assemble it from a few tiles
>that you may have to download separately.
>
>Walter
>
>On Aug 9, 2014, at 1:50 PM, Gregory (Greg) Brenn <[email protected]<m=
ailto:[email protected]>>
>wrote:
>
>> Hello,
>>
>> New user of GMT here, and I'm attempting to create a map of Costa Rica
>>and overlay coastlines and earthquake locations.  Here is my Script:
>>
>> #!/bin/bash
>>
>> clear
>>
>> xyz2grd COSTARIC-6565.xyz -Gcostarica.grd -R-87/-84/9/11 -I2m -V
>>
>> grdimage costarica.grd -JM12 -K -Cmy-topo.cpt -R-87/-84/9/11 >> map.ps<h=
ttp://map.ps/>
>>
>> pscoast -V -O -K -JM -R -W1 >> mappy.ps<http://mappy.ps/>
>>
>> psxy loc.txt -JM12 -R-87/-84/9/11 -Sc.1 -G'45/59/100' -B1/1 -O >> map.ps=
<http://map.ps/>
>> gv map.ps<http://map.ps/>
>>
>>
>>
>> I am using a generic color palette which I can change easily, but the
>>coastlines are extremely low quality, and the topography is extremely
>>pixelated.
>>
>> I look at images in papers, and there's extremely high quality
>>topographic images of COsta Rica, for example, as well as the coastlines
>>and bathymetry, but I have no idea where I can get this high-quality
>>data.  I have tried to get ETOPO data, but I cannot seem to find where
>>to get high-quality data.
>>
>> So I guess my question is, is ETOPO1 the best place to get high-quality
>>topo data, because I cannot seem to figure out how to download data from
>>their website.  Also, would I need to download coastline data, as well?
>>
>>
>>
>> Thanks,
>>
>> Greg
>>
>> Mailing list for GMT discussions of all kinds. If you are not sure you
>>have found a bug, discuss it here first. To formally report bugs or
>>request features, please register and add New Issue on
>>gmt.soest.hawaii.edu<http://gmt.soest.hawaii.edu/> To unsubscribe, send t=
he message "signoff gmt-help"
>>to [email protected]<mailto:[email protected]> Note: gmt-=
help will become obsolete on Sept
>>1, 2014 - please use forum on gmt.soest.hawaii.edu<http://gmt.soest.hawai=
i.edu/> instead.
>
>Mailing list for GMT discussions of all kinds.  If you are not sure you
>have found a bug, discuss it here first.
>To formally report bugs or request features, please register and add New
>Issue on gmt.soest.hawaii.edu<http://gmt.soest.hawaii.edu/>
>To unsubscribe, send the message "signoff gmt-help" to
>[email protected]<mailto:[email protected]>
>Note: gmt-help will become obsolete on Sept 1, 2014 - please use forum on
>gmt.soest.hawaii.edu<http://gmt.soest.hawaii.edu/> instead.

Mailing list for GMT discussions of all kinds.  If you are not sure you hav=
e found a bug, discuss it here first.
To formally report bugs or request features, please register and add New Is=
sue on gmt.soest.hawaii.edu<http://gmt.soest.hawaii.edu/>
To unsubscribe, send the message "signoff gmt-help" to [email protected]=
i.edu<mailto:[email protected]>
Note: gmt-help will become obsolete on Sept 1, 2014 - please use forum on g=
mt.soest.hawaii.edu<http://gmt.soest.hawaii.edu/> instead.

Mailing list for GMT discussions of all kinds. If you are not sure you have=
 found a bug, discuss it here first. To formally report bugs or request fea=
tures, please register and add New Issue on gmt.soest.hawaii.edu<http://gmt=
.soest.hawaii.edu/> To unsubscribe, send the message "signoff gmt-help" to =
[email protected]<mailto:[email protected]> Note: gmt-help =
will become obsolete on Sept 1, 2014 - please use forum on gmt.soest.hawaii=
.edu<http://gmt.soest.hawaii.edu/> instead.

Mailing list for GMT discussions of all kinds.  If you are not sure you have found a bug, discuss it here first.
To formally report bugs or request features, please register and add New Issue on gmt.soest.hawaii.edu
To unsubscribe, send the message "signoff gmt-help" to [email protected]
Note: gmt-help will become obsolete on Sept 1, 2014 - please use forum on gmt.soest.hawaii.edu instead.