Map generation with pointcloud/depth and gps

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Hi, I am working on an outdoor robot for environmental mapping. There is a stereocamera and an RTK GPS on board but the robot has no preexisting knowledge of the environment. I found a lot of documentation and examples about SLAM localization and map building. However, I have no lidar

Can point cloud / depth data and GPS position data be used for mapping an unknown environment and thus to generate a map?

And another question.

If, after initial mapping, the robot uses the generated map for the next bringup, but the initial pose is not inside the map area, is there a possibility to extend the map to the newly learned area?

Any help is very much appreciated.