There are lots of different sources of elevation data around the world. Opentopography has a decent selection of datasets https://www.opentopography.org/
USGS through its 3D Elevation Program (3DEP) has a huge collection of free high-res terrain data: https://apps.nationalmap.gov/3depdem/
This is written from Australia and so examples in these pages will use the awesome ELVIS portal from the good folks of Geoscience Australia. https://elevation.fsdf.org.au/ Resolution varies but there are some really high resolution datasets, some above cities, some above forests and allow a vast array of uses for free.
On the https://elevation.fsdf.org.au/ ELVIS website, at the top left, ‘Layers’ can be changed to display OpenStreetMap for example, which can make it easier to find an area of interest. Once at your area of interests, at the top right, click ‘Order data’. Click on Draw, and then move your cursor to the map area and draw a rectangle over your area of interest (ELVIS has a limit of size per query. For big area you’ll need to do multiple queries). Click Search.
Depending on the area, multiple layers will be returned, different state offering different things. The resolution of a DEM translates into the size of its pixels in the real world. A 50cm DEM will have each pixel giving the elevation of a 50cm2 area on the ground, which is currently one of the highest resolution available. 1m is very good too. 5m and 10m are good too but suits different purposes.
Once the high-res DEM is selected, enter your details, and click download. You will then receive a link via email.
