Open source map development

When creating a web or app map is becoming more popular to use open source maps and own map layers.  Here are some things to get you started.

So in open source I would say there are two big players, Leaflet and OpenLayers.
Google maps is also an alternative but cost money depending on how much you use them, you can calculate cost here.
If you need something simpler I would go with Leaflet or Google but if you need something more advanced I would go with Openlayers.

Gecoding

Geocoding is when you translate coordinates to address or address to coordinates. 

• Google API, https://developers.google.com/maps/documentation/geocoding/start/ ) The most popular due to Google’s name. Extensive support available on the internet (less development time). Alas! not available freely for commercial usage. The free version has 2500 queries/day limitations. There is one clause in “Usage Terms” which says the result must be displayed in google maps, reference terms and conditions are mentioned here. http://code.google.com/apis/maps/terms.html#section_10_12
• Nominatium, (http://wiki.openstreetmap.org/wiki/Nominatim ) A less common organization which provides an open source, free ware solution for the address to (latitude, longitude) mapping. Can be also used in commercial projects. There are no restrictions for number of queries per day and no hidden clauses in “usage terms”. Since the organization itself is not much popular, less support is available.
• Yahoo API, http://developer.yahoo.com/geo/placefinder/ Another popular API like google’s but some what more available. supports upto 50000 requests per day. Like google extensive support is available. Yahoo encourages us to use the “powered by yahoo logo” but doesn’t force us for that. ( http://info.yahoo.com/legal/us/yahoo/api/api-2140.html ) Can be used for commercial purposes (I have read Yahoo Terms and doesn’t find any clause which restricts us in doing that, reference http://info.yahoo.com/legal/us/yahoo/maps/mapsapi/mapsapi-2141.html ).

Geoserver

One of the benefits of using a Geoserver is that they are really fast on rendering a lot of points on maps. Let’s say you have 10 000 points you want to show, it would be really slow on a javascript based map to render all 10 00 points, even worse if you want custom markers.

Query a Geoserver layer

Geoservers even supports CQL (Common Query Language).
It is a human-readable query language, and its syntax is very similar to SQL syntax, but simpler.

CQL supports following operators:

• Comparison operators: =, <>, >, >=, <, <=
• Id, list and other operators: BETWEEN, BEFORE, AFTER, LIKE, IS, EXISTS, NOT, IN
• Arithmetic expression operators: +, -, *, /
• Geometric operators: EQUALS, DISJOINT, INTERSECTS, TOUCHES, CROSSES, WITHIN, CONTAINS, OVERLAPS, RELATE, DWITHIN, BEYOND

GeoServer User Manual has some CQL filter examples, like:

• PERSONS > 15000000
• PERSONS BETWEEN 1000000 AND 3000000
• STATE_NAME = 'California'
• STATE_NAME LIKE 'N%'
• MALE > FEMALE
• UNEMPLOY / (EMPLOYED + UNEMPLOY) > 0.07
• STATE_NAME IN ('New York', 'California', 'Montana', 'Texas')
• BBOX(the_geom, -90, 40, -60, 45)

There might be some difficuties when quering dates depending on formats:

And I haven’t found any support for case insensitve search. 

Markers

Geoservers also have a good support for custom markers. 
You can use built in styles like circle, square, lines etc. 
And you can upload or create your own .SLD file which is a standard styling xlm file which can look something like this: 

<?xml version="1.0" encoding="UTF-8"?>
<StyledLayerDescriptor version="1.0.0" xmlns="http://www.opengis.net/sld" xmlns:ogc="http://www.opengis.net/ogc"
  xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://www.opengis.net/sld http://schemas.opengis.net/sld/1.0.0/StyledLayerDescriptor.xsd">
  <NamedLayer>
    <Name>redflag</Name>
    <UserStyle>
      <Name>burg</Name>
      <Title>A small red flag</Title>
      <Abstract>A sample of how to use an SVG based symbolizer</Abstract>

<FeatureTypeStyle>
   <Rule>
     <Name>Large</Name>
     <MaxScaleDenominator>160000</MaxScaleDenominator>
       <PointSymbolizer>
         <Graphic>
           <ExternalGraphic>
             <OnlineResource
               xlink:type="simple"
               xlink:href="map_icon.png" />
             <Format>image/png</Format>
           </ExternalGraphic>
              <Size>
                32
              </Size>
         </Graphic>
       </PointSymbolizer>
            <TextSymbolizer>
         <Label>
           <ogc:PropertyName>name</ogc:PropertyName>
         </Label>
         <Font>
           <CssParameter name="font-family">Verdana</CssParameter>
           <CssParameter name="font-size">12</CssParameter>
           <CssParameter name="font-style">normal</CssParameter>
           <CssParameter name="font-weight">normal</CssParameter>
         </Font>
         <LabelPlacement>
           <PointPlacement>
             <AnchorPoint>
               <AnchorPointX>0.5</AnchorPointX>
               <AnchorPointY>0.0</AnchorPointY>
             </AnchorPoint>
             <Displacement>
               <DisplacementX>0</DisplacementX>
               <DisplacementY>-28</DisplacementY>
             </Displacement>
           </PointPlacement>
         </LabelPlacement>
         <Fill>
           <CssParameter name="fill">#000000</CssParameter>
         </Fill>
       </TextSymbolizer>
   </Rule>
   <Rule>
     <Name>Medium</Name>
     <MinScaleDenominator>160000</MinScaleDenominator>
     <MaxScaleDenominator>3200000</MaxScaleDenominator>
     <PointSymbolizer>
       <Graphic>
         <Mark>
           <WellKnownName>circle</WellKnownName>
           <Fill>
             <CssParameter name="fill">#CC3300</CssParameter>
           </Fill>
         </Mark>
         <Size>8</Size>
       </Graphic>
     </PointSymbolizer>
   </Rule>
   <Rule>
     <Name>Small</Name>
     <MinScaleDenominator>3200000</MinScaleDenominator>
     <PointSymbolizer>
       <Graphic>
         <Mark>
           <WellKnownName>circle</WellKnownName>
           <Fill>
             <CssParameter name="fill">#CC3300</CssParameter>
           </Fill>
         </Mark>
         <Size>4</Size>
       </Graphic>
     </PointSymbolizer>
   </Rule>
 </FeatureTypeStyle>
    </UserStyle>
  </NamedLayer>
</StyledLayerDescriptor>

That style will create a red dot when zoomed out, when zooming in a bit the dot will change size, and even closer it will change to image and also display a queried label from that position, if you have that data saved on the geoserver of course.