If I am creating data from satellite imagery, is this classed as primary or secondary data?
If I am creating slope data from a DTM, is this then classed as primary or secondary data?
The distinction between primary and secondary data is in where the data originated from.
The article linked below states that any data that is created is primary data. However, in your case, you are deriving data from existing primary data. Based on comments above, there is some controversy about whether data derived from primary data is still considered primary data or not.
With regard to data sources, data can be put into one of two distinct categories. The first category is called primary data. Primary data refer to data that are collected directly or on a firsthand basis. For example, if you wanted to examine the variability of local temperatures in the month of May, and you recorded the temperature at noon every day in May, you would be constructing a primary data set. Conversely, secondary data refer to data collected by someone else or some other party. For instance, when we work with census or economic data collected and distributed by the government, we are using secondary data.