prefilter bad results before adding details and reranking

[nominatim.git] / docs / api / Faq.md

diff --git a/docs/api/Faq.md b/docs/api/Faq.md
index 6bc5b5e831c4cb4adac8adca089aa8e283f7a32d..c4a64d849b80d6947ae7ecd3ba019ede4be6b42f 100644 (file)
--- a/docs/api/Faq.md
+++ b/docs/api/Faq.md
@@ -7,11 +7,11 @@
 Nominatim computes the address from two sources in the OpenStreetMap data:
 from administrative boundaries and from place nodes. Boundaries are the more
 useful source. They precisely describe an area. So it is very clear for
 Nominatim computes the address from two sources in the OpenStreetMap data:
 from administrative boundaries and from place nodes. Boundaries are the more
 useful source. They precisely describe an area. So it is very clear for

-Nominatim if a point belongs to an area of not. Place nodes are more complicated.
-These are only points without any precise extend. So Nominatim has to take a
-guess and assume that an address belongs to the closest place nose it can find.
+Nominatim if a point belongs to an area or not. Place nodes are more complicated.
+These are only points without any precise extent. So Nominatim has to take a
+guess and assume that an address belongs to the closest place node it can find.

 In an ideal world, Nominatim would not need the place nodes but there are
 In an ideal world, Nominatim would not need the place nodes but there are

-many places on earth where there are not precise boundaries available for
+many places on earth where there are no precise boundaries available for

 all parts that make up an address. This is in particular true for the more
 local address parts, like villages and suburbs. Therefore it is not possible
 to completely dismiss place nodes. And sometimes they sneak in where they
 all parts that make up an address. This is in particular true for the more
 local address parts, like villages and suburbs. Therefore it is not possible
 to completely dismiss place nodes. And sometimes they sneak in where they


@@ -21,7 +21,7 @@ As a OpenStreetMap mapper, you can improve the situation in two ways: if you
 see a place node for which already an administrative area exists, then you
 should _link_ the two by adding the node with a 'label' role to the boundary
 relation. If there is no administrative area, you can add the approximate
 see a place node for which already an administrative area exists, then you
 should _link_ the two by adding the node with a 'label' role to the boundary
 relation. If there is no administrative area, you can add the approximate

-extend of the place and tag it place=<something> as well.
+extent of the place and tag it place=<something> as well.

 
 #### 2. When doing reverse search, the address details have parts that don't contain the point I was looking up.
 
 
 #### 2. When doing reverse search, the address details have parts that don't contain the point I was looking up.
 


@@ -30,12 +30,12 @@ Reverse does not give you the address of the point you asked for. Reverse
 returns the closest object to the point you asked for and then returns the
 address of that object. Now, if you are close to a border, then the closest
 object may be across that border. When Nominatim then returns the address,
 returns the closest object to the point you asked for and then returns the
 address of that object. Now, if you are close to a border, then the closest
 object may be across that border. When Nominatim then returns the address,

-contains the county/state/country across the border.
+it contains the county/state/country across the border.

 
 #### 3. I get different counties/states/countries when I change the zoom parameter in the reverse query. How is that possible?
 
 This is basically the same problem as in the previous answer.
 
 #### 3. I get different counties/states/countries when I change the zoom parameter in the reverse query. How is that possible?
 
 This is basically the same problem as in the previous answer.

-The zoom level influences at which [search rank](https://wiki.openstreetmap.org/wiki/Nominatim/Development_overview#Country_to_street_level) Nominatim starts looking
+The zoom level influences at which [search rank](../customize/Ranking.md#search-rank) Nominatim starts looking

 for the closest object. So the closest house number maybe on one side of the
 border while the closest street is on the other. As the address details contain
 the address of the closest object found, you might sometimes get one result,
 for the closest object. So the closest house number maybe on one side of the
 border while the closest street is on the other. As the address details contain
 the address of the closest object found, you might sometimes get one result,


@@ -45,12 +45,12 @@ sometimes the other for the closest point.
 
 Nominatim assigns each map feature one country. Those outside any administrative
 boundaries are assigned a special no-country. Continents or other super-national
 
 Nominatim assigns each map feature one country. Those outside any administrative
 boundaries are assigned a special no-country. Continents or other super-national

-administrations (e.g. European Union, NATO, Custom unions) are not supported, 
+administrations (e.g. European Union, NATO, Custom unions) are not supported,

 see also [Administrative Boundary](https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative#Super-national_administrations).
 
 #### 5. Can you return the timezone?
 
 see also [Administrative Boundary](https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dadministrative#Super-national_administrations).
 
 #### 5. Can you return the timezone?
 

-See this separate OpenStreetMap-based project [Timezone Boundary Builder](https://github.com/evansiroky/timezone-boundary-builder)
+See this separate OpenStreetMap-based project [Timezone Boundary Builder](https://github.com/evansiroky/timezone-boundary-builder).

 
 #### 6. I want to download a list of streets/restaurants of a city/region
 
 
 #### 6. I want to download a list of streets/restaurants of a city/region
 


@@ -58,4 +58,28 @@ The [Overpass API](https://wiki.openstreetmap.org/wiki/Overpass_API) is more
 suited for these kinds of queries.
 
 That said if you installed your own Nominatim instance you can use the
 suited for these kinds of queries.
 
 That said if you installed your own Nominatim instance you can use the

-`/utils/export.php` PHP script as basis to return such lists.
+`nominatim export` PHP script as basis to return such lists.
+
+#### 7. My result has a wrong postcode. Where does it come from?
+
+Most places in OSM don't have a postcode, so Nominatim tries to interpolate
+one. It first look at all the places that make up the address of the place.
+If one of them has a postcode defined, this is the one to be used. When
+none of the address parts has a postcode either, Nominatim interpolates one
+from the surrounding objects. If the postcode is for your result is one, then
+most of the time there is an OSM object with the wrong postcode nearby.
+
+To find the bad postcode, go to
+[https://nominatim.openstreetmap.org](https://nominatim.openstreetmap.org)
+and search for your place. When you have found it, click on the 'details' link
+under the result to go to the details page. There is a field 'Computed Postcode'
+which should display the bad postcode. Click on the 'how?' link. A small
+explanation text appears. It contains a link to a query for Overpass Turbo.
+Click on that and you get a map with all places in the area that have the bad
+postcode. If none is displayed, zoom the map out a bit and then click on 'Run'.
+
+Now go to [OpenStreetMap](https://openstreetmap.org) and fix the error you
+have just found. It will take at least a day for Nominatim to catch up with
+your data fix. Sometimes longer, depending on how much editing activity is in
+the area.
+