Normal Sudoku rules apply.
A line in a cell indicates the presence of a surveyor digit. A digit N is a surveyor if, in the direction of the line, the cells containing N-1 and N+1 are N cells apart. For instance, 3 is a surveyor in 2354 because 2 and 4 are 3 cells apart.
Furthermore, if the line is red, the surveyor is between the two cells it surveys, as in the example above. Otherwise, the line is gray.
All the possible surveyors are given.
Solution code: Column 3, column 7
on 4. June 2023, 21:28 by stephane.bura
Added missing line in the Penpa version.
Thanks DiMono!
on 14. August 2021, 11:34 by Mody
Hat Spaß gemacht. It was funny :)
on 6. October 2020, 22:23 by henrypijames
Ye know, ye could've used arrows instead of lines. ;)
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:D
on 2. October 2020, 21:54 by stephane.bura
Added a line. Thanks Yohann!
on 2. October 2020, 00:04 by marcmees
Appears more dangerous than it really is. Nice. thanks