[Answer]-GeoDjango create model with LineStringField with buffer

So after digging and rethinking all day long I’ve come up with some implementation ideas:

1. Instead of adding buffer to each LineString which will make it a
   Polygon (waste of data space?) and perform a point search for a relevant Polygon with a
   given Point, after going over again on PostGIS ST_Buffer’s docs
   (Geom.buffer on GeoDjango) I understood a better (and faster) use for future queries would be
   with PostGIS ST_DWithin ( <field>__<distance
lookup>=(<geometry>, <distance value>[, 'spheroid']) on
   GeoDjango GeoQuerySets) and by that storing a Segment or street in this case would be with LineString.

2. Thanks to this post, I’ve come up with this piece of code:

   class Sign(models.Model):
       name = models.CharField(max_length=10)
       gps_point = models.PointField()
       objects = models.GeoManager()
   
       def __unicode__(self):
           return self.name
   
   class Segment(models.Model):
       start_sign = models.ForeignKey(Sign, related_name='seg_start')
       end_sign = models.ForeignKey(Sign, related_name='seg_end')
       line = models.LineStringField(blank=True, null=True)
       objects = models.GeoManager()
   
       def save(self):
           super(Segment,self).save()
           if not self.line and self.start_sign and self.end_sign:
               self.line = LineString(self.start_sign.gps_point,self.end_sign.gps_point)
               self.save()
   

   so by overriding save() I could assign LineString(self.start_sign.gps_point,self.end_sign.gps_point) to LineStringField once save is done.
   Now all I have to deal with is assigning a start sign for segment’s start point and end sign for segment’s ending and the LineString object will be created for me 🙂

3. So now I can just filter out the relevant street/segment just by Segment.objects.filter(line__distance_lte=(Point(lat,lon),D(m=required_distance)).

Cheers