I am creating a small land use map, as an exercise for visual image interpretation. I created a shapefile and started digitising polyogons with the polygon tool. The problem is that some of my polygons are automatically simplified/generalised. Some of the vertices disappear as soon as I finish sketch, which makes my map not very accurate.
Then, I also noticed that merging the polygons simplifies them. I just select polygons and click merge, then I notice gaps between them, some of the vertices having disappeared.
I searched the ArcGIS help, as well as online, to see if there are any editing options that I could change to disable this automatic simplification / generalisation, but I could not find any clear answers, only info about tools that can be used to deliberately achieve this effect. I just want ArcMap to leave my vertices where I put them.
This is my first editing attempt in ArcMap 10.2.
I haven't come across this problem in ArcMap 10.1.
EDIT: I am including some further information.
From my Data frame properties:
Map units: Unknown Units
Display: Decimal degrees
Current coordinate system: No coordinate system.
As background image for my polygon shapefile I am using a scanned true color photo (23X23 cm), scale 1:10,000, in the form of a tiff file, with the following properties:
Columns and Rows: 5959, 5573
Cell Size (X.Y): 4.2333418e-005, 4.2333418e-005
Spatial Reference: undefined
Regarding the tolerance, the only types of tolerance that I have set in ArcGIS so far are the "snapping tolerance" and the "sticky move tolerance". I assume that in your comments you are talking about the X,Y tolerance, about which the ArcGIS Help says it has a default value of 0.001 meters (?)
Best Answer
It is close to 0 percent likely this photo is in DD.
1) Define the spatial reference of the background image in ArcCatalog.
2) Ensure it aligns with some other dataset (say from arcgis online) in ArcMAP.
3) Create a blank polygon in ArcCatalog.
4) Define the projection of 3 in ArcCatalog.
5) Start a blank mxd in ArcMap.
6) Add (1) the image with the projection defined.
7) Add (3) the polygon with the projection defined.
8) Start editing and you should be good to go.
numbers 1 and 2 are key.