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Points not all showing on map. Google maps; scatter chart; longitude, latitude; Postcodes; GIS

Hi all,

I have a problem that needs solving; I would be very grateful for any help on the matter.

I have a dynamic background image of Google Maps (London) in a scatter chart. I have a list of 5500 records of buildings in London, with postcodes (and other details). I have also, a comprehensive list of 300,000+ lines of London postcodes - complete with longitude and latitude coordinates.

I have joined the tables together - so that each record of a building, with its postcode, corresponds to a point on the map - the location of which is determined by its longitude and latitude. When no queries are made i.e. no records are selected - I just have a broad view of London with about 1000 blue dots in their locations.

When I make certain queries (in plain English: "Show me all buildings that are owned by ABC Corporation, located in Hackney"), there may be 50+ records of buildings - yet the map shows only 10 dots. Similarly, for some queries on one particular XYZ company, there are 3 records - but 0 dots appear on the map. The map zooms in to the correct location, so far that I can even see the street names of the district, but the dots just simply don't appear on the map.


I have used some code gathered from the trusty internet. Eg. the definition of my QlikView longitude is:

=sum( round (256*pow(2,($(var_zoom)-1)))+( longitude  *((256*pow(2,$(var_zoom)))/360)) ).

I have created unique IDs for each record (dtID); when I select a single dtID of a record from a table box of information - the dot appears. But this only works for individual records. I cannot select the dtIDs of 3 records and have three more dots appear. If I select 3 dtIDs from 3 records - I just get a similar problem. The map zooms in to the correct location but the points do not show.

The points that do not appear tend to have the same postcode. But this is not always the case. E.g. if I have 250 records from a query, there may only be 50 unique postcodes - but I still do not get 50 dots as I would expect. I may only get 20 dots in this case.

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