test_ind = test_ind+1;

	% position to extract from map for testing
	matchpos = zuniq(test_ind);
	
	% extract a test set from the map data
	if (test_ind==2),
		strip
	else,
		% afterward, map is ready; only need to extract test vectors
		testindices = find(zoriglong == matchpos);
		tzp = zpos(testindices);
		tzd = zdirs(testindices);
		tsonars = sonars(testindices);
	end
	
	% compute the set of valid votes
	votes
	
	% tally the votes and plot it
	tally
	
	% plot the data in one display
	clf;
	blackwhite

	ih = imagesc([ll_r, rr_r], [ll_i, rr_i], svt);
		% not sure why, but image likes to flip/flop x & y axes
	set(gca,'YDir','normal')
	hold on;
	quiver(real(mzp),imag(mzp),-real(mzd)*200,-imag(mzd)*200,0,'g');
	plot(real(max_spot), imag(max_spot), 'wx');
	plot(real(matchpos), imag(matchpos), 'k+');

	% print out the error result
	the_error = abs(matchpos-max_spot);
	disp(sprintf('thin_mod = %d   test_ind = %d  the_error = %f', thin_mod, test_ind, the_error));

	% integrate the new data with the map data *using computed position*
	tzp = tsonars.*tzd+max_spot;
	mzp = [ mzp , tzp ];
	mzd = [ mzd , tzd ];
	quiver(real(tzp),imag(tzp),-real(tzd)*400,-imag(tzd)*400,0,'r');