Comparing multi spectral data sets over time.

PIX4Dmapper PIX4Dmapper Questions/Troubleshooting
1

I am looking to compare two multi spectral data sets of the same area taken two months apart.

In an attempt to look at ways of adding value for turf management I am needing to compare data to determine the change in vegetative health over time.

My thinking here is that “benchmarking” the data within the index calculator would allow me to continually compare data of the same area time and time again. ie. using the NDVI formula I could set a particular value, such as 0.89, as healthy and 0.66 as unhealthy. Therefore by using 32 classes and equal area option I know have a base or benchmark against which to compare all future data captured across this given area.

In theory this seems like a logical and accurate way of achieving my objective however I am unaware of the ways to practically generate this within the software. Would I need to work with the two current sets within the same project (is this possible?) and then bring all future sets within the original project going forward? Essentially stacking data and applying all NDVI comparisons across all the board?

I may have over complicated the process but am unaware of any other way. My overall goal is to continually display to my client the changing health of his turf asset over time. Currently I can display shifting areas of variability through processing the sets individually and generating an NDVI with 32 classes and equal area however the direct comparison is necessary to fulfill the desires of my client to enable practical management solutions as the turf health changes over time.

2

Dear Stuart,

If I understood correctly, you want to compare several datasets as a timeline. This is possible visually using our cloud application, as described here, no need to merge all data into the same project. If you want to compute different metrics based on NDVI, for example the difference between 2 NDVI maps taking at different days, you can use some tools like QGIS where you can load the NDVI maps as layers and compute specific metrics (difference between layers, histogram normalization, etc.).

Best regards,

3

Hi Manuel,

As I read it only data from Sequoia is able to be viewed and manipulated in the cloud application. Are data sets from other sensors supported?

Thanks

 

4

Hi Stuart,

Normally, if you can read and process it from the mapper, you can process it also with the cloud. There was a limitation, where the timeline was working only for Sequoia, but not anymore. As long as the meta information are recognized by the mapper (as described here: wavelength, band names, etc.), the NDVI can be computed from the Cloud.

Best regards,