Use this tool (if not using https://osbot.org/api/org/osbot/rs07/api/map/constants/Banks.html#LUMBRIDGE_LOWER) like Explv mentioned.
https://explv.github.io/
Makes your life 10x easier; so qucik to make sections and obscure shapes if needed. Would highly recommend it I use it all the time :p
Great for choosing areas quickly; including Z-/Z+ levels etc. Saves you having to login; put on the settings for coords, mark down the area etc
Also have search feature which is pretty nifty is you don't know the RS map too well.