def load_file(session, source_file, batch_size=100, userid=None):
utcnow = util.utcnow()
utcmin = utcnow - datetime.timedelta(120)
with open(source_file, 'r') as fd:
reader = csv.reader(fd, delimiter='\t', quotechar=None)
counter = 0
items = []
for fields in reader:
try:
time = int(fields[0])
if time == 0: # pragma: no cover
# unknown time gets an old date
time = utcmin
else:
# convert from unixtime to utc
time = datetime.datetime.utcfromtimestamp(time)
key = normalized_wifi_key(str(fields[1]))
if not valid_wifi_pattern(key): # pragma: no cover
continue
lat = float(fields[2])
lon = float(fields[3])
accuracy = int(fields[4])
altitude = int(fields[5])
altitude_accuracy = int(fields[6])
channel = int(fields[7])
signal = int(fields[8])
wifi = dict(
key=key,
channel=channel,
signal=signal,
)
data = dict(
lat=lat,
lon=lon,
time=time,
accuracy=accuracy,
altitude=altitude,
altitude_accuracy=altitude_accuracy,
radio='',
cell=(),
wifi=[wifi],
# not sure if the importer has an actual file
# specification anywhere
heading=-255,
speed=-255,
)
except (ValueError, IndexError):
continue
items.append(data)
counter += 1
# flush every batch_size records
if counter % batch_size == 0:
process_measures(items, session, userid=userid)
items = []
session.flush()
print('Added %s records.' % counter)
# process the remaining items
process_measures(items, session, userid=userid)
print('Added %s records.' % counter)
session.flush()
return counter
def search_wifi(session, data):
# Estimate signal strength at -100 dBm if none is provided,
# which is worse than the 99th percentile of wifi dBms we
# see in practice (-98).
def signal_strength(w):
if 'signal' in w:
return int(w['signal'])
else:
return -100
wifi_signals = dict([(normalized_wifi_key(w['key']),
signal_strength(w))
for w in data['wifi']])
wifi_keys = set(wifi_signals.keys())
if not any(wifi_keys):
# No valid normalized keys.
return None
if len(wifi_keys) < MIN_WIFIS_IN_QUERY:
# We didn't get enough keys.
return None
query = session.query(Wifi.key, Wifi.lat, Wifi.lon, Wifi.range).filter(
Wifi.key.in_(wifi_keys)).filter(
Wifi.lat.isnot(None)).filter(
Wifi.lon.isnot(None))
wifis = query.all()
if len(wifis) < MIN_WIFIS_IN_QUERY:
# We didn't get enough matches.
return None
wifis = [Network(normalized_wifi_key(w[0]), w[1], w[2], w[3])
for w in wifis]
# Sort networks by signal strengths in query.
wifis.sort(lambda a, b: cmp(wifi_signals[b.key],
wifi_signals[a.key]))
clusters = []
# The first loop forms a set of clusters by distance,
# preferring the cluster with the stronger signal strength
# if there's a tie.
for w in wifis:
# Try to assign w to a cluster (but at most one).
for c in clusters:
for n in c:
if distance(quantize(n.lat),
quantize(n.lon),
quantize(w.lat),
quantize(w.lon)) <= MAX_WIFI_CLUSTER_KM:
c.append(w)
w = None
break
if w is None:
break
# If w didn't adhere to any cluster, make a new one.
if w is not None:
clusters.append([w])
# The second loop selects a cluster and estimates the position of that
# cluster. The selected cluster is the one with the most points, larger
# than MIN_WIFIS_IN_CLUSTER; its position is estimated taking up-to
# MAX_WIFIS_IN_CLUSTER worth of points from the cluster, which is
# pre-sorted in signal-strength order due to the way we built the
# clusters.
#
# The reasoning here is that if we have >1 cluster at all, we probably
# have some bad data -- likely an AP or set of APs associated with a
# single antenna that moved -- since a user shouldn't be able to hear
# multiple groups 500m apart.
#
# So we're trying to select a cluster that's most-likely good data,
# which we assume to be the one with the most points in it.
#
# The reason we take a subset of those points when estimating location
# is that we're doing a (non-weighted) centroid calculation, which is
# itself unbalanced by distant elements. Even if we did a weighted
# centroid here, using radio intensity as a proxy for distance has an
# error that increases significantly with distance, so we'd have to
# underweight pretty heavily.
clusters = [c for c in clusters if len(c) > MIN_WIFIS_IN_CLUSTER]
if len(clusters) == 0:
return None
clusters.sort(lambda a, b: cmp(len(b), len(a)))
cluster = clusters[0]
sample = cluster[:min(len(cluster), MAX_WIFIS_IN_CLUSTER)]
length = len(sample)
avg_lat = sum([n.lat for n in sample]) / length
avg_lon = sum([n.lon for n in sample]) / length
return {
'lat': quantize(avg_lat),
'lon': quantize(avg_lon),
'accuracy': estimate_accuracy(avg_lat, avg_lon,
sample, WIFI_MIN_ACCURACY),
}
def search_wifi(session, data):
# estimate signal strength at -100 dBm if none is provided,
# which is worse than the 99th percentile of wifi dBms we
# see in practice (-98).
def signal_strength(w):
if 'signal' in w:
return int(w['signal'])
else:
return -100
wifi_signals = dict([(normalized_wifi_key(w['key']),
signal_strength(w))
for w in data['wifi']])
wifi_keys = set(wifi_signals.keys())
if not any(wifi_keys):
# no valid normalized keys
return None
if len(wifi_keys) < 3:
# we didn't even get three keys, bail out
return None
query = session.query(Wifi.key, Wifi.lat, Wifi.lon).filter(
Wifi.key.in_(wifi_keys)).filter(
Wifi.lat.isnot(None)).filter(
Wifi.lon.isnot(None))
wifis = query.all()
if len(wifis) < 3:
# we got fewer than three actual matches
return None
wifis = [Network(normalized_wifi_key(w[0]), w[1], w[2]) for w in wifis]
# sort networks by signal strengths in query
wifis.sort(lambda a, b: cmp(wifi_signals[b.key],
wifi_signals[a.key]))
clusters = []
for w in wifis:
# try to assign w to a cluster (but at most one)
for c in clusters:
for n in c:
if distance(quantize(n.lat), quantize(n.lon),
quantize(w.lat), quantize(w.lon)) <= MAX_DIST:
c.append(w)
w = None
break
if len(c) >= 3:
# if we have a cluster with more than 3
# networks in it, return its centroid.
length = len(c)
avg_lat = sum([n.lat for n in c]) / length
avg_lon = sum([n.lon for n in c]) / length
return {
'lat': quantize(avg_lat),
'lon': quantize(avg_lon),
'accuracy': 500,
}
if w is None:
break
# if w didn't adhere to any cluster, make a new one
if w is not None:
clusters.append([w])
# if we didn't get any clusters with >3 networks,
# the query is a bunch of outliers; give up and
# let the next location method try.
return None
