Hi, in which spectral bands do you want to map? Also are you asking about flight height, image overlap and the likes or UAV models? Please make your query a little bit detailed. I'm currently working on a related work and could share my observation.

thanks

Before we can answer your question we need to know:

What are you trying to measure/quantify/detect?

What kind of sensor you have (camera)?

Keep in mind, cheap UAVs have low resolution sensor.

Dear Essayas and Mounir am very appreciating. Actually I want to use visible spectral band and NIR  also about the flight height and overlapping I  dont know yet but it should be 20-30% side and forward 60%. and I intent to use high spatial resolusion image? I hope these detail will help you to get understand about what I want. Thank you very much to both of you

Thanks  for detailing Hayder! Let me put my experience on the issues you mentioned and we may continue the conversation once you start your mapping. A 20-30% side and a 60% forward overlap is a trivial choice. As long as you do not generate a DEM you should not be worried about the extent of the overlap. Your main concern regarding the overlap should be a complete coverage of your study area. But on the other hand you need to orthorectify the images and hence you need to generate either the DEM or DTM to do the orthorectification.

Second, the flight height is an important parameter. Unfortunately the flight height is constrained by aviation regulators. In the US for example you can't fly a UAV higher than 400 feet (i.e. about 120 meters). Then comes the size of your smallest object you want to map in the study area. Your image resolution should be half of the size of the minimum mapping unit. If you are going to do quantitative remote sensing make sure that the image processing suit provided with the UAV produces reflectance raster. Some UAVs have sensors whose measurement could not be converted to reflectance and this poses problems if you intend to perform quantitative remote sensing. A major challenge in UAV remote sensing is the image processing. Make sure that you have 1) Precise ground control points (GCPs) and 2) good capacity computer. Hope this will help.

best