Messages

1

Feature Requests / How to use Sequoia calibration target with Photoscan

« on: January 24, 2017, 07:33:55 PM »

You have photos of the target taken with the camera? One option is to apply radiomateric correction after to the mosaic in a GIS (raster calculator) or image processing program.

(1) Obtain histogram of ROI from photos of target - one for each channel of the image
(2) Determine relations (at simplest level, ratios) of target known reflectance or albedo value and intensity from histogram
(3) Apply these ratios as correction values to each channel of mosaic (or in equation for vegetation index).

2

General / Instructions for CIR Calibration? Experience with results?

« on: November 28, 2016, 04:52:44 AM »

Hi

Where can one find practical instructions / guidelines for CIR calibration for estimating radiometric corrections of channels for vegetation indices?

Can the Auto model procedure be run on a selection of a mosaic (e.g. neutral reflectance target)?

I read somewhere in this forum, that the Auto model assumes that the camera blue channel is used for NIR and that some senstivity to NIR is assumed in the other two channels. Obviously, these assumptions may not be met...

Does anyone have experience and can comment on suitability of the CIR calibration for NDVI calculations using Photoscan's raster calculator.

3

General / Re: Agisoft and Micasense RedEdge Processing

« on: July 22, 2016, 01:15:18 AM »

Hello Alexey

Unfortunately, spatial coregistration errors of even as little as 1-2 pixels will lead to incorrect vegetation Index maps.

One could think of processing each band separately, and then doing a coregistration in other software; however, I suppose it is quite possible that individual bands would differ spatially if different lens parameters are used, also leading to errors.

Do you know of any plans in the (very) near future to introduce between-band spatial coregistration in Photoscan processing?

There is an increasing availability of such multiple lens cameras on the market (at least 4 at this time that I am aware of), being used for purposes of e.g. NDVI map creation.

regards,
Dvoralai

4

General / Re: Agisoft and Micasense RedEdge Processing

« on: July 21, 2016, 11:43:38 AM »

Hi Alexey

Thanks for your reply.

I would like to confirm that I inderstand you correctly. You state that
"PhotoScan will assume that all images related to the individual bands were taken from the same camera position, but the orientation may be different as well as lens parameters." yet strictly speaking the 5 bands are not taken from exactly the same position because of physical lens displacement, and not just a rotation. Can the lens parameters account for a relative translation of bands, the coregistration I enquiries about?

D

5

General / Agisoft and Micasense RedEdge Processing

« on: July 13, 2016, 12:52:04 PM »

Is Agisoft Photoscan Pro able to accurately corregister the individual channels of fixed-frame multi-lens cameras such as the micasense rededge or parrot sequioa? If so, any specific settings or workflow to follow for such cameras?

It is important for vegetation índex Calculations, for example, that the resulting multi-channel mosaic has all bands properly aligned in space. Even a few pixels displacement may produce incorrect índices.

I have found a number of posts on the forum where users have had problems processing missions, but none reporting success...

Dvoralai

6

General / Multispectral mosaic blending

« on: June 15, 2016, 02:15:42 AM »

Hullo

Very interested in hearting about experiences and obtaining advice on best method to use to  blend mosaics (blending, average, disabled) for "accurate" NDVI map creation rfom Agisoft mosaics.
For
(1) modified consumer-grade cameras (e.g. maxmax products) - JPEG vs RAW images
(2) multispectral cameras such as the micasense rededge, parrot sequioa
(3) tetracam ADC cameras

We are using the maxmax Canon SX230 HS and SX260 HS (always in manual mode with infinite focus, fixed f-stop value, fixed ISO, fixed exposure time) and in general getting NDVI maps that groundtruthing indicates provide correct patterns of relative NDVI (after reflectance calibration of channels) from Orthos created using Mosaic blending - but occasionally the maps show variations in NDVI that may just arise from flightline directions.

One can expect that blending mode will still be important when using "true" multispectral cameras to capture images.

7

Feature Requests / Reflectance calibration

« on: June 15, 2016, 02:06:17 AM »

Excellent that Photoscan Professional nowe permits vegetation index calculation using raster caluclator. It would be extremely valuable to add a Reflectance Calibration module, for mosaics creayed using images that have not been radiometrically corrected at the time of image capture.
Common procedure is to identify areas in mosaic with known reflectance (such as scenes with one or more reflectance targets) to generate a correction equation for each channel so that pixel intensity (DN) is mapped to the approximate reflectance value.
Then allow "automatic" application of correction factor to each channel for the raster calculator.
Such a feature is important for generating more accurate NDVI (ore relative NDVI) and other veg index maps.

8

General / Agisoft Vs Competitors

« on: May 08, 2015, 05:42:12 PM »

Hi Wishgranter

I have a Tetracam ADC project I was able to process with pix4dmapper and get a high quality mosaic. Be happy to provide you the images (RAW or processed TIF?) to see whether you can get a mosaic using Photoscan Pro (I was not able to) and pass on details of steps/parameters.

9

General / Agisoft Vs Competitors

« on: May 07, 2015, 07:53:22 PM »

I have tested both pix4d and agisoft for numerous projects (aerial imaging of orchards and horticultural row crops using both modified Canon powershots and Tetracam ADC). And fuerthermore done extensive groundtruthing of NDVI maps created from mosaics. Both have their advantages and disadvantages.

In favor of Agisoft:

Price if you only need one license and will use all year round. pix4d price includes 2 licenses and also provide options for monthly rentals.

Notably better quality mosaics in terms of intensity values.
Can (after reflectance calibration) create a NDVI map from the mosaic that reflects general patterns well.
pix4dmapper produces many artefacts in the mosaic (stripes of differing intensity for example) and it is necessary to create a reflectance map from the mosaic for index calculations - another procesing step (and time!) and the output formats are not readable by standard image processing programs.

Setting up images (adding, deleting, dynamic links between screens) much more flexible.

More control over parameters of processes. With experience can get good solutions just as rapidly or even faster than pix4dmapper.


In favor of pix4dmapper:

Better job aligning chunks (even without GCPs in many cases). In both, better to avoid mutiple chunks if possible.

Better technical support. Always get a reply and followup from technical support staff. With Agisoft, seems to be a roulette whether you get any response at all.

Easier for non-technical people to use (a target market for pix4dmapper)

Provide satellite map background - often useful for project setup

Comprehensive camera database, easily updated

Can process Tetracam ADC images; although mosaics have serious quality problems due to limitations of this camera. Have not been able to successfully process any Tetracam ADC projects using Agisoft to date.

On a related note, better documentation.

We have also presented a conference paper comparing (some aspects) of the two programs; available to any interested.

10

General / Tetracam adc multispectral camera processing AGAIN

« on: May 05, 2015, 09:48:50 PM »

Hi

It would be most helpful if detailed instructions for processing Tetracam ADC aerial images (latest Photoscan Pro version) could be posted.

I have the same problems reported by others on this forum (images not aligning, and the plane of the model built from those that do is oriented about 90 degrees from where it should be) and I have tried following instructions posted in several places on this forum as well as other methods.

None of these work:

(1) Batch export RAWs to TIFs using PixelWrench2 and using these in Photoscan
(2) Batch export RAWs to multi-page TIFs using PixelWrench2  (setting NIR channel 1 as master channel in Photoscan Pro).
(3) PixelWrench2/TifExport the above created multipage TIFs as per instructions in this forum -- PixelWrench2 creates 16 bit images (images have one channel only, makes no difference if use default or channel 1 as master).

Like others have lamented, (3) is not working, and similarly wondering 'what am i doing wrong?´

Note: locations are available for all images and there should well be sufficient overlap (about 65% lateral, 80% longitudinal).

p.s. I have been looking to purchase Agisoft Photoscan Pro as an alternative to a rival orthomosaicing software that we have been using to date but where we are unsatisfied with the quality of mosaics for NDVI calculations (as verified by field scouting) - but that depends on being able to use Photoscan to process TTC images (which the other product can do). Photoscan os doing a good job with images from digital cameras (including modified ones), but TTC processing is proving a bummer.