[Qgis-developer] Style Editor request

[Howard, Stephen]

I sent this request earlier with an attachment (screen shots) and received
back an email advising the email was too big (greater than 80KB)

here it is again without the attachment

Hello Qgis developers…
I have a request for an enhancement to the style editor for raster images,
or if you know this feature already exists as a plug-in or in a more recent
release (I’m working with 2.8), please let me know)

Some background…. I work for the US Geological Survey on projects that map
fires and burn severity using Landsat imagery (see http:\\mtbs.gov). We are
unable to map all fires and know that many local fire managers would like
to map fires that we cannot due to time and budget constraints.  All of our
MTBS processing uses proprietary software.

With funding support from NASA and the US National Park Service we are
developing a Qgis plug-in to allow users to perform a Landsat image-based
burn severity assessment.

One of the important steps in the process requires the user to visually
evaluate a signed 16-bit gray-scale image known as the Differenced
Normalize Burn Ratio (dNBR). Higher dNBR values correspond with higher burn
severity, and there is a dNBR value that corresponds to a threshold between
burned and unburned vegetation.

During this visual evaluation, the user is trying to determine the
burned/unburned and high severity thresholds in the dNBR image. These vary
from fire to fire and the process is essentially a trial and error effort
where user selects a threshold value, colors the dNBR pseudo-color image
and compares it to the satellite image or a copy of the original dNBR.

In the ERDAS/Imagine software package, the raster attribute editor allows
the user to display the entire range of dNBR values in pseudo color.  Then,
using the mouse/cursor or “Criteria” (e.g. values >= 100) the user can
select a large range of values and color code them all at once.

In QGIS style editor, the user can also display the dNBR image in
pseudo-color, but the user must specify the number of “classes” to show,
from 5 to perhaps hundreds.  5 is too few and even 50 is too many because
the user may only select one class at a time to assign a color rather than
a range of classes.  So the more classes (gray scale levels) the user
chooses for gray scale resolution, the more tedious it becomes to color
code the classes.

Enhancement request:   Allow the user to select multiple pseudo-color
classes at one time. A “left-click select” followed by a “shift left-click
select” would be sufficient.

Enhancement request: Allow the elements in the display area of QGIS to be
manipulated (zoom, change display order etc) while the “properties/style”
interface is open.  During the interpretation process, it helps to be able
to make these manipulations without having to close then reopen the style
interface.

We hope to release our plugin in early 2017, and I am writing up a
user-guide describing the step-by step process to order Landsat imagery,
pre-process it, and subsequent steps to interpret the dNBR using the
plug-in we’re developing.

I can send jpgs showing a dNBR.tif and the final classified image
(_dnbr6.tif) and some screen shots of style editor and the dNBR imagery.  A
pseudo-color image would provide more precision if the number of class
intervals were set 100. (The min and max of -200 to 800 was set by me
because I already knew the range of relevant dNBR values for this fire.
Note the full range of dNBR values is -1454 to 1750 and for the final
pseudo-color image I changed the max changed to 1400 to fill in the values
above 800 ).

The 6 class dNBR image was created using thresholds interpreted using
ERDAS/Image Raster attribute editor, the thresholds are <80 (unburned, Dark
Green), 80 (burned not burned) 81 – 420 (low severity), 421 – 775 (moderate
severity, yellow) and >775 (high severity, red)

Thanks for your consideration of this request.

If you have any questions, please do not hesitate to contact me. I can send
screen shots if that would help.

Please acknowledge receipt of this request by return email.   Thanks again.

Steve.


-- 
****************************
Stephen M. Howard
USGS, EROS
47914   252nd St
Sioux Falls, SD  57198
tel:  605 594 6027
email: smhoward at usgs.gov
<https://mail.google.com/mail/?view=cm&fs=1&tf=1&to=smhoward@usgs.gov>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20160808/3533c566/attachment.html>