OpenTopography is a valuable resource for high-resolution, Earth science-oriented topography data and related tools. It hosts most of the NZ Lidar data. OpenTopography is particularly useful when the 1m DEMs provided on LINZ Data Service lack detail in an area of interest. OpenTopography allows you to create DEMs directly from lidar data at the resolution of your choice. If you’re new to OpenTopography, take some time to explore their resources and tools. They have a series of helpful videos on their YouTube channel,including this video about generating DEMs. That particular video might be all you need to get you going, but I’ve provided a few tips below on my process for your reference..
Start by visiting the OpenTopography website. Look for the ‘Data’ tab in the navigation bar at the top of the page. This is where you’ll find all the available datasets. The ‘Find Data Map’ is particularly useful. Use the map to look up your area of interest. Alternatively, you can search for data by region, dataset type, or project name in the data catalog. Once you’ve found the dataset you want to download, click on the ‘Point Cloud Data’ button under the ‘Download and Access Products’ tab.
Once you’ve selected your dataset, you’ll need to prepare your data for download. First, restrict the area you want to download by using the ‘Select a Region’ button. Then, under the ‘Choose Return Classification’ section, make sure you select the appropriate returns - you probably only want to select the ground returns and uncheck all the other returns.
Under the ‘DEM Generation’ section, you’ll need to specify your grid size in the ‘Gridding Parameters’. This is where you can set a slightly higher resolution than usual. The maximum resolution you want to set should be based on the point cloud density. Assuming that the points are evenly distributed across the area, the maximum grid density can be calculated using the square root of the inverse of the point cloud density. Here’s the formula:
DEM Resolution=
The resulting raster resolution is in the same units as the point cloud density. For example, if the point cloud density is in points per square meter, the raster resolution will be in meters.
Enter your email and job name, and you will be alerted when the download is ready!
This video shows how to create and download data from OpenTopography.
You will receive an email with a link to the data. The data will be in a tarball format, which you will have to extract twice using software such as 7Zip. You will end up with a raster format file. You should be able to import this directly into your preferred GIS software!