Processing of Point Cloud data with different CRS fails.

[Ron-Simpson]

When an area to be mapped has Point Cloud tiles with different CRS (EPSG:28355 & EPSG:28356) the GUI fails.
There is a manual work around but it would be preferable to automate it if possible.
The manual work around is to

• Reproject the Point Cloud tiles so that they have the same CRS (e.g. reproject the EPSG:28356 to EPSG:28355)
• Merge the original ESPG:28355 tiles and the reprojected tiles
• Run the GUI with the merged tiles

The third step is necessary because there can be a large overlap of the CRS which will result in Blaze creating duplicated contours (which is visible on the map) if the tiles are not merged.

https://1drv.ms/f/c/7a156ebb815df146/IgBZKe-3J9DLSbrp-6rgopnFAQZPxQidXvUa3nEDSPYIaCw?e=frKtDX link to tiles with differing CRS

[ryanstocks00]

This is a known issue that I also encountered whilst generating the 2025 IB maps. Unfortunately, the Blaze program currently does not do any sophisticated projection management and simply sets the projection of outputs to match the projection of the input, fully operating within the projected coordinate system. This has the side effect that all input tiles must have the same CRS. It also assumes that the tiles do not overlap as you have discovered. Both of these are non-trivial to fix so this will likely sit on the backburner for a while unless someone else is more determined to fix it. Similar issues will likely be encountered if using non-uniform tiles.

I suspect the best way to fix this is to load all of the tile extents and projections at the beginning of the program, then if multiple CRSs are encountered, ask the user which projection to use and internally produce a set of virtual tile extents for the full extent in this projection. Then for each virtual tile extent, load the data from all of the input lidar files that overlap the virtual tile and convert to the output projection before proceeding.

For now, there are two workarounds:

1. For smaller areas, merge all lidar files before running Blaze and run it on a single area as you have identified
2. For large areas, run Blaze separately for the tiles in each CRS region and combine manually in QGIS (for the IB maps I set an extent in QGIS that I wanted to be UTM 55 and the remainder UTM 56 and trimmed any contours etc. outside that region to eliminate the duplicated contours)