Putting Crime Data on a Map Mark Patrick Business Unit Manager
advertisement
Putting Crime Data on a Map www.esriuk.com Mark Patrick Business Unit Manager Crime and Disorder Unit ESRI (UK) Ltd crime + disorder ESRI (UK) Putting Crime Data on a Map www.esriuk.com What are these? How much do I need? How do I know? crime + disorder What’s this about? Which one ESRI (UK) and how? Coordinates www.esriuk.com • • • • • • • Majority of crimes happen at a location Need for common referencing system Unique description of each location Many different ways of describing a location using coordinates Most commonly these are either geocentric or projected systems Projected coordinates system works well in UK Small size and shape of UK means only small amount of distortion introduced crime + disorder ESRI (UK) British National Grid www.esriuk.com • A projected coordinate system that covers Great Britain • Separate grids exist for Ireland • 91 grid squares, each 100km • Each referenced by a 2 letter code crime + disorder ESRI (UK) British National Grid www.esriuk.com Northings 500,000 300,000 100,000 0 Metres East, 0 Metres North crime + disorder 100,000 300,000 500,000 Eastings ESRI (UK) British National Grid www.esriuk.com TL The TQ square is 100km x 100km Its origin is :500000 E 100000 N SU TQ TR 100,000 TV crime + disorder 500,000 ESRI (UK) British National Grid www.esriuk.com The TQ square is divided Into a grid of 100 10km squares The reference of this square Is 510000 E 110000 N TQ 100,000 500,000 crime + disorder ESRI (UK) British National Grid www.esriuk.com The 10km squares can be divided into 1Km squares giving another level of precision. The red 10km square has coordinates of 510000 170000 The blue square is therefore at 513000 175000 500,000 crime + disorder ESRI (UK) British National Grid www.esriuk.com • Levels of Precision Reference TQ 500000 510000 512000 512700 512750 512571 100000 130000 135000 135600 135690 135692 Precision 100km 100km 10km 1km 100m 10m 1m crime + disorder ESRI (UK) Putting Crime Data on a Map www.esriuk.com What are these? How much do I need? How do I know? crime + disorder What’s this about? Which one ESRI (UK) And how? Fit for purpose? www.esriuk.com • Levels of Precision Reference TQ 500000 510000 512000 512700 512750 512571 100000 130000 135000 135600 135690 135692 Precision 100km 100km 10km 1km 100m 10m 1m • Depends on the analysis… • Murder rates in world cities • Town centre street robbery crime + disorder ESRI (UK) Putting Crime Data on a Map www.esriuk.com How much do I need? How do I know? crime + disorder What’s this about? Which one ESRI (UK) And how? How much of an address do I need? www.esriuk.com • Depends on the analysis again… ~ Murder rates in world cities ~ Town centre street robbery • The more detail the better ~ ~ ~ ~ ~ ~ • Street Number / Organisation name Street Name Locality Town Postcode Location description? Queen’s Park Harvest Road Kilburn London NW6 6NN Near the bandstand Completeness, accuracy and spelling crime + disorder ESRI (UK) Putting Crime Data on a Map www.esriuk.com How much do I need? crime + disorder What’s this about? Which one ESRI (UK) And how? Geocoding www.esriuk.com • • • A data matching process Matching addresses to a lookup table Appending coordinates St Num Street Town Postcode 49 Hatfield Close London SE14 5DW OSAPR AP3MAP8U0D4456M0DT APUJAP8U5D3456M0DT APFG0B8F7D3456U0PJ AP3MAP8U6D4456M0DT APUJAP8B5D3456M0ET APFG0B8F0D3456U0PJ APU80B8F5D7455UGPJ APU80B8F6D7455UGPJ APU80B8F7D7455UGPJ APU80B8F0D7455UGPJ SF RV DP ON crime + disorder BN S BD 0058 0059 0060 0061 0062 0063 0049 0050 0051 0052 TN REASTON STREET REASTON STREET REASTON STREET REASTON STREET REASTON STREET REASTON STREET HATFIELD CLOSE HATFIELD CLOSE HATFIELD CLOSE HATFIELD CLOSE X 5355807 Y 1771367 DR PT DL DD CN PC X LONDON SE145DT LONDON SE145DT LONDON SE145DT LONDON SE145DT LONDON SE145DT LONDON SE145DT LONDON SE145DW LONDON SE145DW LONDON SE145DW LONDON SE145DW Y 5355210 5355173 5355115 5355210 5355173 5355115 5355807 5355807 5355807 5355807 ESRI (UK) 1772257 1772198 1772164 1772257 1772198 1772164 1771367 1771367 1771367 1771367 Geocoding www.esriuk.com • • OS ADDRESS-POINT MasterMap Address Layer • • Derived from the Postal Address File (PAF) Spatial reference for 26 million residential and commercial premises crime + disorder ESRI (UK) Precision and Accuracy www.esriuk.com • Precision ~ ~ ~ ~ Relates to measurement and repeatability “A stones throw from the junction with … “ “34.5 metres south of the junction with …” Precision is NOT the same as accuracy ~ The precision of ADDRESS-POINT is sub-metre ~ It is not always 100% accurate crime + disorder ESRI (UK) Precision and Accuracy www.esriuk.com • Accuracy ~ ~ ~ ~ ~ Accuracy is about truth It is NOT the same as precision How close is the information to reality There is both spatial accuracy and attribute accuracy ADDRESS-POINT may have sub metre precision, but it has some accuracy issues “Accuracy is telling the truth . . . Precision is telling the same story over and over again” crime + disorder ESRI (UK) Geocoding Problems www.esriuk.com • • 26 million records in ADDRESS-POINT Input data quality ~ ~ ~ ~ • • Spelling Formatting Completeness Abbreviation Postcodes ADDRESS-POINT crime + disorder ESRI (UK) ADDRESS-POINT www.esriuk.com crime + disorder ESRI (UK) ADDRESS-POINT www.esriuk.com crime + disorder ESRI (UK) ADDRESS-POINT www.esriuk.com crime + disorder ESRI (UK) In defence of ADDRESS-POINT www.esriuk.com • • • • 26 million records in ADDRESS-POINT Business’s change faster than AP is updated Use the positional accuracy flags In the vast majority of cases, AP is spot on • Thanks to OS crime + disorder ESRI (UK) Putting Crime Data on a Map www.esriuk.com crime + disorder ESRI (UK)
