# [GRASS-user] v.patch drops adjacent polygons

A. Marcia BARBOSA anamarciabarbosa at gmail.com
Fri Jun 5 11:52:12 EDT 2009

```> What does v.info on the two vectors and the patched vector say in terms
> of extends and number of objects, in this case only boundaries,
> centroids, areas, islands?

\$ v.info map=utm10_3132
[...]
|   Number of points:       0               Number of areas:      43280      |
|   Number of lines:        0               Number of islands:    1          |
|   Number of boundaries:   87166           Number of faces:      0          |
|   Number of centroids:    43280           Number of kernels:    0          |
[...]
|         Projection: Lat/Lon                                                |
|               N:  72:05:57.201093N    S:  27:05:25.520375N                 |
|               E:               12E    W:                 0                 |

\$ v.info map=utm10_3334

|   Number of points:       0               Number of areas:      43280      |
|   Number of lines:        0               Number of islands:    1          |
|   Number of boundaries:   87174           Number of faces:      0          |
|   Number of centroids:    43280           Number of kernels:    0          |

|         Projection: Lat/Lon                                                |
|               N:  72:05:57.201093N    S:  27:05:25.520375N                 |
|               E:               24E    W:               12E                 |

\$ v.info map=utm10_31to34     # patched map

|   Number of points:       0               Number of areas:      85544      |
|   Number of lines:        0               Number of islands:    0          |
|   Number of boundaries:   174340          Number of faces:      0          |
|   Number of centroids:    86560           Number of kernels:    0          |

|         Projection: Lat/Lon                                                |
|               N:  72:05:57.201093N    S:  27:05:25.520375N                 |
|               E:               24E    W:                 0                 |

So, both input maps have the same number of polygons and centroids (as
expected), but different number of boundaries - is this normal? The
original maps were shapefiles that I imported with v.in.ogr. Should I
do any additional cleaning of topology? Also he two inputs have an
island each, but the output has none.

The geographic limits are as expected for two longitudinally adjacent
tiles. And the output has the sum of the number of centroids of the
two inputs, but less areas...