Avoid timestamps in trajectory IDs

[anitagraser]

Currently, e.g. after clipping, the trajectory IDs in the trajectory dfs include timestamp information. This should be replaced with cleaner IDs, like in the to_traj_gdf output:

import geopandas as gpd
import movingpandas as mpd
from shapely.geometry import Polygon

gdf = gpd.read_file("../sample_data/geolife.gpkg")
tc = mpd.TrajectoryCollection(gdf, traj_id_col="trajectory_id", t="t")

poly = Polygon.from_bounds(116.343,39.900,116.373,39.914)
clipped = tc.clip(poly)
clipped.to_point_gdf()

clipped.to_traj_gdf()