Get field value in custom searchcomponent (solr 3.3)

[Pablo Ricco]

What is the best way to get a float field value from docID?
I tried the following code but when it runs throws an exception For input
string: "`??eI" at line float lat = Float.parseFloat(tlat);

schemal.xml:
...
    <fieldType name="float" class="solr.TrieFloatField" precisionStep="0"
omitNorms="true" positionIncrementGap="0"/>
...
    <field name="latitude" type="float" indexed="true" stored="true"
multiValued="false" />

component.java:

@Override
public void process(ResponseBuilder rb) throws IOException {
DocSet docs = rb.getResults().docSet;
SolrIndexSearcher searcher = req.getSearcher()
FieldCache.StringIndex slat =
FieldCache.DEFAULT.getStringIndex(searcher.getReader(), "latitude");
DocIterator iter = docs.iterator(); while (iter.hasNext()) {
 int docID = iter.nextDoc(); String tlat = slat.lookup[slat.order[docID]];
if (tlat != null) {
 float lat = Float.parseFloat(tlat); //Exception!
}
}
}

Thanks,
Pablo