Bug #1127
sph2grd
| Status: | Closed | Start date: | 2017-07-06 | |
|---|---|---|---|---|
| Priority: | Normal | Due date: | ||
| Assignee: | - | % Done: | 0% | |
| Category: | - | |||
| Target version: | Candidate for next bugfix release | |||
| Affected version: | 6.x-svn | Platform: | Linux |
Description
Running gmt 5.4.0 on ubuntu 16.04.
I'm generating grids with sph2grd, for example with L=10, M=5, C=1, S=0. When setting the normalistaion flag to -Ng, I get grids who's inner products sum to 4*pi. However, when the flag is -Nm, they appear to sum to 0.5 rather than 1.
History
#1
Updated by Paul about 4 years ago
- Status changed from New to Feedback
- Target version set to Candidate for next bugfix release
Would you mind showing how you computed the 0.5 so I can make a test script for this. I am looking at the code and find
if (ortho)
plm[mm] = pmm * 0.5 / d_sqrt(M_PI);
so that 0.5 is suspicious in light of your post. But I'd like to verify first.
#2
Updated by Mark about 4 years ago
res="1" # deg - resolution of SH grid
pi="3.141592"
echo "Integrated Ylm**2 volume = "$(gmt grd2xyz sh.grd | awk 'BEGIN {sum=0} {sum+=(sin((90-$2)*'$pi'/180)*'$res'*'$res'*('$pi'/180)*('$pi'/180)*($3^2))} END {printf "%.6f\n", sum}')
#3
Updated by Remko about 4 years ago
Indeed the factor "0.5" should be "1.0". Fixed now in both trunk and branch.
#4
Updated by Remko about 4 years ago
- Status changed from Feedback to Resolved
#7
Updated by Paul 6 months ago
- Affected version changed from 5.x-svn to 6.x-svn
This is definitibvely not the place to report anything anymore - please use www.generic-mapping-tools.org for a portal to all things GMT, including the GitHub site where bugs and issues can be reported.
Looking at the code there are in fact two places where the plm[mm] = pmm * 0.5 / d_sqrt(M_PI);
type expressions appear, and it looks like Remko only fixed one as there is another where the 0.5 still lives. I will fix that in master now. You will need to build and test to be sure of send me a simple script that I can use to verify the result.