public static void fillSearchParameterBox(@NonNull final Map<String, String> valueMap, @NonNull final Parameters params, @Nullable final Viewport viewport) {

        final String bboxString = GeopointFormatter.format(GeopointFormatter.Format.LAT_DECDEGREE_RAW, viewport.bottomLeft)
                + SEPARATOR + GeopointFormatter.format(GeopointFormatter.Format.LON_DECDEGREE_RAW, viewport.bottomLeft)
                + SEPARATOR + GeopointFormatter.format(GeopointFormatter.Format.LAT_DECDEGREE_RAW, viewport.topRight)
                + SEPARATOR + GeopointFormatter.format(GeopointFormatter.Format.LON_DECDEGREE_RAW, viewport.topRight);
        valueMap.put("bbox", bboxString);

        fillSearchParameterCenter(valueMap, params, viewport.getCenter(), DEFAULT_RADIUS);
        params.removeKey("search_method");
        params.put("search_method", METHOD_SEARCH_BBOX);
    }
Client for the OpenCaching API (Okapi).

@see <a href="http://www.opencaching.de/okapi/introduction.html">Okapi overview</a>
main/src/main/java/cgeo/geocaching/connector/oc/OkapiClient.java